senior project report - cal poly
TRANSCRIPT
Senior Project Report
June 5, 2015
Cable Drag Test System
Sponsored by:
Specialized Bicycle Components, Inc.
Prepared by:
Smooth Shifters
Alex Powers – [email protected]
Brandon Roy Sadiarin – [email protected]
George Rodriguez – [email protected]
Torey Kruisheer – [email protected]
Statement of Disclaimer
Since this project is a result of a class assignment, it has been graded and accepted as fulfillment of the
course requirements. Acceptance does not imply technical accuracy or reliability. Any use of
information in this report is done at the risk of the user. These risks may include catastrophic failure of
the device or infringement of patent or copyright laws. California Polytechnic State University at San
Luis Obispo and its staff cannot be held liable for any use or misuse of the project.
Table of Contents
Chapter 1. Introduction ............................................................................................................................... 1
Chapter 2. Background ............................................................................................................................... 1
Cables and Related Hardware ................................................................................................................. 1
Cable Size, Structure and Housing Differences .................................................................................. 2
Patents and Similar Existing Systems ..................................................................................................... 3
Verizon Patent and Licensing, Inc. ..................................................................................................... 3
Cable Tension Tester .......................................................................................................................... 4
Cable-Conduit System Model ............................................................................................................. 5
Components That Contribute to Cable Drag .......................................................................................... 6
Bosses: ................................................................................................................................................ 6
Stops:................................................................................................................................................... 7
Donuts: ................................................................................................................................................ 7
Dropout Guide: ................................................................................................................................... 7
Bottom Bracket Guide: ....................................................................................................................... 8
Command Post: ................................................................................................................................... 9
Cable on cable interaction:.................................................................................................................. 9
The House of Quality ............................................................................................................................ 11
Physical Specification Parameters ........................................................................................................ 12
Operation Parameters ............................................................................................................................ 12
Performance Parameters ....................................................................................................................... 13
Simulation Parameters .......................................................................................................................... 13
Chapter 3. Design Development ............................................................................................................... 13
Decision Matrices ................................................................................................................................. 13
Preliminary Top Concepts .................................................................................................................... 14
Initial Technical Considerations ........................................................................................................... 18
Intermediate Designs ............................................................................................................................ 18
Single Magnetic Base to Dual Magnetic Base Redesign .................................................................. 18
80/20 T-slot Design........................................................................................................................... 19
Rotary Potentiometer Positioning System ........................................................................................ 20
Chapter 4. Description of Final Design .................................................................................................... 20
Main Base ............................................................................................................................................. 21
Dual Magnetic Base and Vertical Slide ................................................................................................ 21
Fixtures ................................................................................................................................................. 22
Handlebar Mimicking Fixture ........................................................................................................... 22
Stem Fixture ...................................................................................................................................... 23
Cable Stops ....................................................................................................................................... 23
Bottom Bracket Guide ...................................................................................................................... 25
Rear Derailleur Mounting Fixture .................................................................................................... 25
Front Derailleur Mounting Fixture ................................................................................................... 26
Brake Fixture .................................................................................................................................... 27
Analysis/Preliminary Testing................................................................................................................ 27
Dual Magnetic Base Analysis & Testing .......................................................................................... 27
Deflection Analysis ........................................................................................................................... 28
Force Measurement ............................................................................................................................... 28
Positional Measurement ........................................................................................................................ 30
Chapter 5. Manufacturing ........................................................................................................................ 31
Main Base Plates ................................................................................................................................... 32
Handlebar Mimicking Fixture ............................................................................................................... 33
Actual Stem Fixture .............................................................................................................................. 35
Cable Stop Fixture ................................................................................................................................ 35
Bottom Bracket Fixture......................................................................................................................... 37
Main Base and Vertical Slide Assembly .............................................................................................. 39
Rear Derailleur ...................................................................................................................................... 40
Front Derailleur ..................................................................................................................................... 41
Brake Fixture ........................................................................................................................................ 41
Chapter 6. Design Verification ................................................................................................................. 42
Time Tests ............................................................................................................................................. 42
Calibration Tests ................................................................................................................................... 42
Comparison Test ................................................................................................................................... 42
Cost Analysis ........................................................................................................................................ 42
Safety Considerations ........................................................................................................................... 44
Chapter 7. Management & Teamwork...................................................................................................... 44
Chapter 8. Testing & Results .................................................................................................................... 46
Chapter 9. Future Recommendations ........................................................................................................ 48
Chapter 10. Conclusion ............................................................................................................................. 49
References ................................................................................................................................................. 50
Appendix A ............................................................................................................................................... 52
QFD....................................................................................................................................................... 52
Decision Matrices ................................................................................................................................. 54
Preliminary Drawings ........................................................................................................................... 58
Preliminary Analysis ............................................................................................................................. 60
Safety Design Checklist ........................................................................................................................ 61
Appendix B ............................................................................................................................................... 63
DRAWING NUMBERS LIST ............................................................................................................. 63
STOP FIXTURE ................................................................................................................................... 64
HANDLEBAR FIXTURE .................................................................................................................... 68
BB GUIDE FIXTURE .......................................................................................................................... 73
FRONT DERAILLEUR FIXTURE ..................................................................................................... 78
REAR DERAILLEUR FIXTURE ........................................................................................................ 79
PARTS THAT NEED TO BE CNC MILLED ..................................................................................... 80
VERTICAL SLIDE ASSEMBLY ........................................................................................................ 84
MEASUREMENT ................................................................................................................................ 87
LOAD CELL ........................................................................................................................................ 89
Appendix C (List of Vendors) .................................................................................................................. 91
Appendix D (Data Sheets) ........................................................................................................................ 92
Appendix E (analysis) ............................................................................................................................. 121
Hand Calculations ............................................................................................................................... 121
Matlab Code: Magnetic Base Analysis ............................................................................................... 126
Display Parameter Figure ............................................................................................................... 126
Double Base Parameters ................................................................................................................. 126
Double Magnetic Base Analysis ..................................................................................................... 127
Single Base Parameters ................................................................................................................... 127
Single Magnetic Base Analysis ...................................................................................................... 127
Print Results .................................................................................................................................... 127
Plotting ............................................................................................................................................ 128
Create mesh ..................................................................................................................................... 128
Design Failure Mode Effects and Analysis ........................................................................................ 130
Appendix F (Gantt Chart) ....................................................................................................................... 133
Appendix G (DVP&R) ........................................................................................................................... 134
Appendix H (Load Cell Calibration) ...................................................................................................... 136
Appendix I (Safety Checklist) ................................................................................................................ 137
Appendix J (Bill of Materials) ............................................................................................................... 138
Appendix K (Procedure) ......................................................................................................................... 140
List of Figures Figure 1. Various types of bicycle cable systems ....................................................................................... 2
Figure 2. Internal structures of brake and shifter cable systems, respectively ........................................... 3 Figure 3. Test apparatus for measuring bending and kink forces in cables ................................................ 4 Figure 4. Representation of a cable tension tester ...................................................................................... 5 Figure 5. Experimental test to model transmission characteristics across a cable-conduit system ............ 6 Figure 6. Boss in the bicycle frame ............................................................................................................ 6
Figure 7. Internal Cable Routing Stops....................................................................................................... 7 Figure 8. Rubber donuts around the cable .................................................................................................. 7 Figure 9. Rear dropout and dropout guide .................................................................................................. 8 Figure 10. Example bottom bracket guide .................................................................................................. 8 Figure 11. Cable routing necessary for command post actuation ............................................................... 9
Figure 12. Implementation of the California Cross in a down tube.......................................................... 10 Figure 13. Preliminary CAD concept of test system, at the close of PDR ............................................... 15
Figure 14. Picture of magnetic base to be used ........................................................................................ 16 Figure 15. Diagram of magnetic base system ........................................................................................... 16 Figure 16. Bottom bracket mounting device............................................................................................. 16 Figure 17. Modular linear rail slider fixture front (left) and back (right) views ....................................... 17
Figure 18. Magnetic base holder ............................................................................................................... 17 Figure 19. 80/20 T-slot design .................................................................................................................. 19
Figure 20. Rotary Potentiometer ............................................................................................................... 20 Figure 21. Final Design Layout ................................................................................................................ 21 Figure 22. Dual magnetic base assembly with vertical slide and rotary plate .......................................... 22
Figure 23. Custom handlebar fixture in assembly and exploded views. .................................................. 23 Figure 24. Cable stop fixture in assembled and exploded views .............................................................. 24
Figure 25. Bottom Bracket guide fixture in assembled and exploded views. ........................................... 25
Figure 26. Rear derailleur fixture with noodle block ................................................................................ 25
Figure 27. Front Derailleur Fixture ........................................................................................................... 26 Figure 28. Braze-On Anchor ..................................................................................................................... 26 Figure 29. Brake Fixture ........................................................................................................................... 27
Figure 30. NI-6001 USB DAQ ................................................................................................................. 28 Figure 31. Interface sealed stainless steel load cell .................................................................................. 29
Figure 32. Load Cell Assembly ................................................................................................................ 29 Figure 33. Interface SGA signal conditioner ............................................................................................ 30 Figure 34. Picture of final layout sent to be water jet cut ......................................................................... 31
Figure 35. Picture of the 10 gauge steel main base plates ........................................................................ 32 Figure 36. Final assembled handlebar mimicking fixture ........................................................................ 34 Figure 37. Bracket for cable stop assembly, with face that needs material removed ............................... 36
Figure 38. Finished cable stop fixture assembly ....................................................................................... 37
Figure 39. Bottom bracket guide arm ....................................................................................................... 38 Figure 40. Finished assembly of the bottom bracket guide ...................................................................... 39 Figure 41. Initial Design of Rear Derailleur Fixture ................................................................................. 40 Figure 42. Completed rear derailleur fixture assembly ............................................................................ 41 Figure 43. Real Tarmac frame and test system comparison ..................................................................... 46
Figure 44. Effect of pretension on required tension force ........................................................................ 47 Figure 45. Difference in shifting profile based on varied cable geometry ............................................... 48
List of Tables Table 1. Engineering specifications for test device .................................................................................. 11
Table 2. Engineering Specifications for Simulation Environment ........................................................... 12 Table 3. Final Cost of Miscellaneous Items.............................................................................................. 43 Table 4. Final Cost of Raw Materials ....................................................................................................... 43 Table 5. Initial and Final Cost Estimates .................................................................................................. 43 Table 6. List of major project milestones and their corresponding dates of completion .......................... 45
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Chapter 1. Introduction
The Smooth Shifters is a team composed of Alex Powers, Brandon Roy Sadiarin, George Rodriguez,
and Torey Kruisheer. We are four senior mechanical engineering students at California Polytechnic
State University (Cal Poly) in San Luis Obispo, California that are working on a senior design project
for Specialized Bicycle Components, Inc. located in Morgan Hill, California. We will be under the
advisement of Professor Sarah T. Harding of the mechanical engineering department at Cal Poly.
Specialized, one of today’s leading bicycle companies, is in need of a test setup that measures brake and
shifter cable drag. High performance cyclists using time trial, triathlon, and aero bikes are constantly
looking for ways to have as much aerodynamic advantage as possible, paired with a low profile look on
their bicycles. To address these issues, bicycle companies have started a new trend of routing cables
inside of the bicycle frames, rather than running them outside the frames. Unfortunately, routing a cable
through a bicycle’s frame causes additional cable drag which ultimately decreases shifting and braking
performance. Specialized has requested a test setup that can be used to determine cable drag in any cable
configuration prior to the fabrication of a physical prototype.
The goals of this project are:
1. To create a physical system to accurately mimic cable routing of a Specialized Tarmac bicycle
frame and a comparative tool to measure the cable drag in competing systems.
2. To create a simulation environment which allows a user to build a cable system to check
performance without a physical test apparatus. A database of different routing systems and
components can then be built up over time for continuous use with different frames.
The purpose of the test is to save time and money, by testing and quantifying cable drag before a
physical prototype is put into production. This test setup will allow for changes in frame geometry to be
made, and will allow the corresponding shifter cable drag to be compared.
Chapter 2. Background
In order to understand the task at hand, we first had to research cable drag itself, its contributing factors,
and why it is important to analyze. Physically, cable drag occurs when a cable is routed in such a way
that the output force at the end of the cable is less than if the cable was routed in a more direct manner.
This leads to less precise shifting, as well as less braking power for a given applied force. The specific
causes of cable drag may be attributed to the various types of cable systems, the group set hardware they
are used with, and the numerous contact points that are inherent in routing a cable both internally or
externally. The following paragraphs are a summary of the key details of our research.
Cables and Related Hardware
The first stage of background research involved determining the different types of cable systems, as well
as their associated hardware. This step was taken in order to familiarize ourselves with the various
components that our end product will use, and to understand how each component contributes to the
overall performance of the cable systems. The cable systems that our end product will test can be broken
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into two different types: brake cable systems and shifter cable systems. These can be differentiated
through their structure, size, and housing differences.
Cable Size, Structure and Housing Differences
Brake cables are typically thicker than shifter/derailleur cables. Brake cables have diameters that range
from 1.5 to 1.6 millimeters, while shifter cables have diameters that are typically 1.1 or 1.2 millimeters
[1]. The differences in size can be seen in Figure 1.
Figure 1. Various types of bicycle cable systems
In Figure 1, a typical brake cable system is labeled A, while a typical shifter cable system is labeled D. Size differences are due to the application for each type of cable system. This is related to the amount of
tension needed for each type of cable system. Brake cable systems need to be stiffer and stronger in
order to be able to produce more power during operation. Shifter cable systems can be more compliant,
in order to have “compressionless” effects that enable riders to have crisp shifting. Differences in cable
system structure can be seen in Figure 2. Due to the differences in the operation of the two types of
cable systems, brake cable systems experience larger forces than shifter cable systems. This directly
affects our end product, as we will have to use different benchmarks when measuring brake cable force
versus measuring shifter cable force.
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Figure 2. Internal structures of brake and shifter cable systems, respectively
Patents and Similar Existing Systems
The second stage of our background research involved patent searches of existing internally routed cable
systems, as well as existing cable force measurement devices and methods. We researched patents in
order to see what similar systems and solutions already exist, and to evaluate their methods of solving
the problem. This is important because it allows us to have some sort of standard or base for developing
ideas that will lead us towards a solution. Although we cannot directly copy the patents’ assemblies and
technologies, we are able to generate ideas easier from this initial patent research rather than starting
from complete scratch. A patent search also shows the state of prior art to ensure our design is not
infringing on any existing patents. For the purpose of this document, we will focus on existing systems
that utilize at least one of the intended functions that our end product will have, such as force
measurement.
Verizon Patent and Licensing, Inc.
In order to install fiber optic cables through ducts, Verizon uses a method called blow-in, or cable jetting
[2]. For effective installation, the cable must meet specific requirements. Verizon has developed an
apparatus that measures a bending and kink force associated with a cable when it is subject to a
bend/kink. A diagram of the apparatus can be seen in Figure 3.
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Figure 3. Test apparatus for measuring bending and kink forces in cables
We have made observations on Verizon’s patent, and have found aspects of the design that we would
like to include in our design, as well as things that could be improved upon. Due to the nature of
patents, we could not identify the true size of Verizon’s test apparatus; however, we noticed that the test
apparatus is only capable of testing a small length of cable. Our system will need to be capable of testing
a much larger test configuration.
What we did like about this test apparatus is its ability to measure a cable’s force when a bend is
present. We would like to be able to expand on that ability so that our end product is able to measure
forces when multiple bends exist within the test cable. We are primarily concerned with accurate
simulation in our test system.
Cable Tension Tester
Another patent that we looked into describes an apparatus specifically for testing cable tension in brake
cables [3].This apparatus tests cables that are subjected to various input tensions. It includes a
comparator which compares the measured tensions in the test cables to reference tension values. A
detailed drawing of the apparatus can be seen in Figure 4.
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Figure 4. Representation of a cable tension tester
The ability to input various tension forces in this design directly correlates with the need for our end
product to be modular and reconfigurable. However, this cable tension tester only operates with lateral
displacement and does not take into account displacement in three dimensions. Our end product needs
to be able to have measurements in all three dimensions, and account for both linear and radial
movements.
Cable-Conduit System Model
A paper published in the Institute of Electrical and Electronic Engineers’ Transactions on Robotics
provides a detailed model of cable-conduit interactions based on cable curvature, tension, and nonlinear
friction [4]. The mathematical model developed in this paper is given by a set of partial differential
equations that can be solved to determine the precise motion and tension transmission in a cable-conduit
system. This is directly applicable to the simulation portion of this project. The mathematical models
developed by Agrawal, Peine, and Yao are a possible method of force analysis, which could be used for
input into the computer simulation.
The model was verified by experimental results from a test set up that is not all that different from a
routing configuration on a bicycle. The experiment included a tensioned cable, a conduit, and cable
curvature; all of which are key factors in realistically modeling cable routing configurations seen on a
bicycle.
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Figure 5. Experimental test to model transmission characteristics across a cable-conduit system
Components That Contribute to Cable Drag
Further research showed how numerous components contribute to cable drag. After speaking with
bicycle technicians, we discovered that tight bend radii, such as those in the handlebars, reduce the
performance of the cables. Furthermore, we discovered that the various components that are in contact
with the cables contribute to the overall cable drag. These components include the following: bosses,
stops, donuts, dropout guides, bottom bracket guides, command posts, and other cables.
Bosses:
Bosses are holes, built into the frame that allow the cables to be guided into the frame. Figure 6
demonstrates how the positioning of the bosses affect the angle at which the cables enter, therefore
affect the bend radii, oftentimes paired with cable on frame rubbing [5].
Figure 6. Boss in the bicycle frame
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Stops:
Stops are used in conjunction with bosses, leading the cable into the bicycle frame and preventing
external dirt or objects out of the frame. Internally Routed Cable (ICR) stops fill the gap that occurs
between the bosses in the frame and the cables themselves. As seen in Figure 7, ICR stops contribute to
the total drag experienced by the cable, as they house the cable and add to hindered performance [6].
Figure 7. Internal Cable Routing Stops
Donuts:
Donuts are rubber pieces inside the top tube of the frame that hold the cables in place, thus reducing the
rattling of the cable within the tube. These donuts come in direct contact with the cables, as seen in
Figure 8 which shows donuts that are representative of what could be seen within the top tube [7].
Figure 8. Rubber donuts around the cable
Dropout Guide:
The dropout tube, located at the point where the seat stay, chain stay, and dropout come together, helps
guide the cable from the internal portion of the chain stay over the dropout. Figure 9 depicts a portion of
a dropout guide easing the cable over the dropout and eventually to the rear derailleur [8].
8
Figure 9. Rear dropout and dropout guide
Bottom Bracket Guide:
The bottom bracket guides, used to positon the shifter cables along the bottom bracket, come in contact
with both the front and rear shifter cables. As demonstrated in Figure 10, the bottom bracket guides rub
on the cables while the bottom bracket itself adds additional curve in the cables [9].
Figure 10. Example bottom bracket guide
9
Command Post:
The command post is an adjustable seat post, with a corresponding remote-actuated saddle positioning
system. The command post allows the rider to easily change the seat height, but requires another cable
routed to the component. Figure 11 shows the geometry a command post cable must navigate through.
The bend that the cable must take to get to the command post is tight and provides additional drag, much
like the front derailleur [10].
Figure 11. Cable routing necessary for command post actuation
Cable on cable interaction:
Cable on cable interaction causes additional drag and is often hard to prevent without adding additional
components which will increase cable bend. Depending on rider preference, cables may be routed to
cross each other to make smoother shifting, with less tight bends in the cable. Figure 12 shows the
“California Cross”, which crosses the cables both externally and internally within the down tube [11].
10
Figure 12. Implementation of the California Cross in a down tube
After more thorough research was conducted following the project proposal, more knowledge about
what contributes to cable drag was acquired. This information can be seen above in the components list,
which was used to identify crucial pieces necessary in our final design.
Group sets from bicycle component manufacturers comprise of different collections of mechanical parts,
such as shifters, brakes, and derailleurs. The question regarding variations in group sets was proposed
and further testing from our team proved that different brands and models of group sets, did in fact
change the overall drag that a system encountered.
Currently, Specialized has no way to efficiently evaluate drag and component wear in different cable
configurations when routing cables through a bicycle frame. Specialized is able to design a frame and
test different cable routing configurations; however, this requires creating and manufacturing a
prototype, which is costly and time consuming. The Smooth Shifters seek to develop testing and
simulation tools in order to analyze the performance of cable systems and related components prior to
prototype production. The main design goals will be:
1. To create a physical system to accurate mimic cable routing of a Specialized Tarmac bicycle
fame internally routed bicycle frame and a tool to measure the drag in the system.
2. To create a simulation environment which allows a user to build a cable system to check
performance without a physical test apparatus. A database of different routing systems and
components can then be built up over time for continuous use with different frames.
While a simulation environment would be very useful for the development of future designs, it is
superseded in priority by the objective of the physical test setup and data acquisition system, thus may
not be completed due to time constraints.
Quality Function Deployment (QFD) and a corresponding house of quality (Appendix A) were
employed to find the relative importance of each requirement, based on existing products and customer
needs. Subsequent engineering specifications with relative risk and compliance were determined and put
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into Tables 1 and 2. This section explains the house of quality and the decisions to be made moving
forward.
The House of Quality
The house of quality has two main sections in the list of requirements: a section for the design Goal 1
requirements, and another section for the design Goal 2 requirements. The relationship symbols in the
middle of the house correlate the engineering specifications with each customer need based on the
strength of their relationship. Appendix A also outlines the meaning of each of these symbols. The left
side of the house outlines the voice of each customer by rating each requirement based on specific
needs.
For our analysis, we took only the opinion of Specialized into account when computing relative
customer requirement weight because the final product is primarily in the interest of Specialized. The
relative weight is a representation of the importance of that specific requirement. It takes the assigned
ranking of the customer requirement and divides by the sum of all rankings.
The right side contains existing products and our evaluation of how well they meet each customer
requirement. This was done to compare our final product with currently available solutions and find
areas for improvement. The bottom contains the target values for the specifications and each relative
weight. The technical importance is used to determine the relative weight of each engineering
specification. It is computed by summing the product of the relative weight of the customer requirement
with each relationship symbol weight.
The following tables list each engineering specification along with its requirement or target to be met,
how that target is to be met (maximum, minimum, etc.), the risk (high, medium, or low), and the
compliance. The compliance includes how each specification will be determined sufficient. Listed is any
combination of A (analysis), T (testing), I (inspection), and S (similarity to existing products).
Table 1. Engineering specifications for test device
Spec.
# Parameter Description
Requirement or
Target Tolerance Risk Compliance
1 Size 3 ft. x 4 ft. Max M A, I
2 Weight N/A Max M A,I
3 Bend Radius Tolerance 1mm Max M A,T
4 Time to Perform One Test 30 minutes Max L T
5 Number of Runs Before
Recalibration 50 Min M T, A
6 Time to Learn How to Use 1 Hour Max L T
7 Measurement Resolution 1 N Max H A, T
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Table 2. Engineering Specifications for Simulation Environment
Spec.
# Parameter Description
Requirement or
Target Tolerance Risk Compliance
1 Computation Time for One Run 1.5 Minutes Max L T, I
2 Expandable Libraries from Test
Data Y/N Min H I, T
3 Time to Create Set-up in GUI 5 Minutes Max M I, T, S
Physical Specification Parameters
The maximum size parameter was modified knowing that the setup needs to be large enough to model a
range of frame sizes. The Preliminary Design Report (PDR) size specification of 6 ft. x 4 ft. has since
been altered to better accommodate the setup of the final design. Taking the largest Specialized wheel
base dimension of 61 inches, and adding an additional 10%, the base length was found to be
approximately four feet long. The height parameter was set to three feet to accommodate the frame
geometry of the Tarmac, making the necessary dimensions approximately 4 ft. x 3 ft. Initially a weight
parameter of 200 lbf was set for the table, but this specification has also changed. A ferrous table that
Specialized already has in house will be used in lieu of the metal plate, therefore the weight parameter is
not of importance. An initial bend radius tolerance of three millimeters to recreate cable drag was set up
after consulting bicycle mechanics, but further discussion with our sponsor yielded a positioning
tolerance of one millimeter, to accurately represent the bends in the cables and the effect that these
bends had on the total cable drag.
Operation Parameters
After interviewing mechanics at a local bicycle shop, we found that it could take anywhere between five
and thirty minutes to internally reroute cables on a bicycle. Alternatively, after routing a frame
ourselves and taking upwards of an hour to complete the job, we quickly realized the intricate
geometries the frame provides. Off hand, we ran into the issue of feeding the cable through the
handlebars when each cable had to take a specific route, independent of one another and the cables
would often interfere with each other. With this information, we made the specification for time to
perform one test thirty minutes to ensure the geometries are accurately portrayed. Because accuracy was
deemed integral for this test setup, the number of runs before recalibration was an important parameter.
We wanted an accurate setup that would perform a number of tests before recalibration was necessary
and fifty runs was decidedly sufficient. This test setup needed to be intuitive and user friendly to people
with some background on bicycle cable routing. Though it should be intuitive, there will likely be
multiple components that would need extra background and information before becoming proficient in
using the setup. All things considered, we made one hour to learn a reasonable amount of time to
acquire the knowledge necessary to operate the test device.
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Performance Parameters
An issue that we found pressing was the accuracy of the testing’s readings, as the tension loads
experienced by bicycle cables are very small. Specialized has requested to have a measurement
resolution of one Newton.
Simulation Parameters
Following our Preliminary Design Report, the scope of the project has continued to change. Though the
simulation is still a possibility at the close of the project, the physical test setup is of paramount
importance. The computation time for one run was determined based on the amount of time that the test
would take as a whole, and a reasonable amount of time to wait solely on computation was one and a
half minutes. Specialized has requested a way to collect and store data in order to use it for future
purposes. We decided that this feature would need to be integrated into the simulation. The amount of
time that it would take to set up the graphical user interface (GUI) was set at five minutes, as we wanted
the simulation to be intuitive and eliminate the need for the physical test setup.
Chapter 3. Design Development
After deciding that the final design would require multiple subsystems to be successful, the first ideation
session was run, implementing a morphological matrix. The morphological matrix allowed for
countless subsystem options to be combined to create a final product. Different ways of attaching
fixtures to the base, accurately recreating 3-D cable geometry, and various ways of measuring force
were listed individually in the morphological matrix. The various columns focused on each problem
individually. Going through each column, many different possibilities can be paired together to get a
design with unique characteristics. Knowing that tight bend radii heavily contribute to cable drag,
accurate cable routing recreation is an important factor for design. One option that resulted from this
session was using cones to vary the bed radii. The cones give a wide range of radii, which can recreate
very subtle curves, or very tight turns. The force measurement ideation resulted in ideas such as using
linear force gauges, torsional measurement, strain gauges, or three-point digital gauges. Though the
morphological matrix method gave many possible results and got the group thinking creatively, many of
the ideas paired together were not feasible. After the morphological matrix, brainwriting was implemented. Mainly focusing on how the force
should be measured, each team member had a piece of paper, and wrote down ideas for measuring the
force and then was passed to the next member, who could further expand upon it. This method allowed
for the development of different ideas to find the most accurate measurement of the force. This also
lead to further research to find the range of resolution that would be needed for measuring shifting and
braking force.
The idea generation phase lead us to break up the design process into multiple facets in order to compare
subsystems of the design.
Decision Matrices The final product’s components were split into four main subsystems: fixture base, fixture connection,
measurement system, and position control. Each of the four subsystems received their own decision
matrix with multiple solutions to the problem. These matrices are shown in full detail in Appendix A.
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Each solution was weighed against the criteria of modularity, ease of use, machinability, set-up time,
cost, lead time, location resolution, and stability.
Starting with the fixture base, the datum was set with a horizontal magnetic base. Horizontal peg hole
and slider bases were considered, but each fell short of the magnetic base in modularity and location
resolution. Vertical orientation of the base was also considered, with a vertical grate and magnetic
vertical grate. The vertically oriented bases did not score as well as the horizontal magnetic base in
machinability or ease of use.
After evaluating the concepts of the base, fixture connections were evaluated, with a dovetail connection
as the datum. Judged off the same criteria as above, magnetic, slots, suction cups, and a chuck were
weighed against the dovetail connection. Magnets scored the highest in the fact that setup time and
location resolution performed better than the other datum. Slots ended up being a viable option as they
are easy to use and comparable to the dovetail in the other criteria. Suction cups on the other hand did
not offer great location resolution or stability, making them a less reliable option for fixture
connection. Lastly, the chuck scored high for modularity, but did not offer a lot in terms of
machinability or cost efficiency.
Using the linear force gauge as the datum, a digital torque measurement, a 3-Point digital scale, a strain
gauge, linear spring deflection, and torsional spring deflection were weighed against each other to see
the pros and cons of each force measurement choice. The digital torque measurement scored low in the
set-up time and measurement resolution criteria, while the 3-Point digital gauge was in line with the
linear force gauge for all criteria. The strain gauge seemed like the least viable option at the completion
of the decision matrix. The strain gauge did not offer a lot of modularity, ease of use, or high
measurement resolution in comparison to the linear force gauge. The torsional and linear spring
deflection methods scored high in the cost criteria, but suffered in other categories such as ease of use
and measurement resolution.
The position control decision matrix was used to determine how the fixtures would be kept in position
once they were placed on the base. Set screws were set as the datum and grid lines, lead screws, rack
and pinion, ball screws, linear actuators, and turntables were each weighed against the set screws. Grid
lines scored highest, as they are easy to use, easily machined, and can be used quickly. Lead screws,
rack and pinion, ball screws, linear actuators, and turntables each scored worse that the set screws. Lead
screws were not cost effective or easy to use, while rack and pinion and ball screws offered a high
measurement resolution but at a high cost. Linear actuators scored low for cost effectiveness and
manufacture time. Turntables on the other hand did not offer the greatest cost effectiveness, but was in
line with the set screws in all other criteria.
Some initial ideas and their drawings that came out of ideation are included as Appendix A.
Preliminary Top Concepts
From our Preliminary Design Report, each subsystem decision matrix was used in pairwise comparison
in finding many solutions to the problem. Though each subsystem decision matrix yielded a highest
scoring concept, when pairing it with other subsystems, oftentimes the highest scorer was not the best
for the entire concept. For example, the horizontal peg hole resulted in the highest score for the base,
but paired with the highest scoring fixture connector, magnets, was not an effective solution. Multiple
options paired together gave feasible solutions, such as the horizontal magnetic base, with magnetic
15
connection fixtures, grid line positioning, and a linear force gauge. This pairing offers modularity, a
quick setup time, and a reliable positioning resolution.
The exercise in creating each decision matrix mentioned previously resulted in a concept of what the
final test set up looked like at the close of the Preliminary Design Report. A concept CAD model is
shown below in Figure 13.
Figure 13. Preliminary CAD concept of test system, at the close of PDR
This model shows an example of what a test setup could look like with the discussed top concepts. The
system includes modular fixtures for derailleurs, brakes, a bottom bracket guide, bosses, and basic cable
guides all fixed to a metal base. The main top concept for the testing system is the culmination of all the
decision matrices and ideation, and stems from a pairwise comparison method used to take the best
concepts from each category and find the best solution. Our final concept here turned out to be a large
horizontal sheet metal base with magnetic bases that can be mechanically turned on and off to fix all the
components to the base. This magnetic base is shown below in Figures 14 [12] and 15 [13] and consists
of two rails of iron on the outside with a strip of non-ferrous material in the middle to create a way to
“switch off” the magnetism to allow for positioning. All other fixtures are attached to these bases with a
set screw on the top of the base.
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Figure 14. Picture of magnetic base to be used
Figure 15. Diagram of magnetic base system
Bottom bracket sizes vary between bikes, and the bottom bracket guides need to guide two cables at the
same radius. Our top concept for this fixture, shown in the assembly and below as Figure 16, is simply a
thin walled cylinder with three set screws that can accommodate a variety of cylinder sizes to simulate
different bottom brackets.
Figure 16. Bottom bracket mounting device
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The fixture used to mount the derailleurs shown in the assembly above in Figure 13 will also be used to
mount brakes and possibly other components if needed. It consists of two magnetic bases to
accommodate two six inch beam rails (attached with brackets) with a sliding block fixture that will be
fixed in place with set screws. The sliding block has multiple tapped M8x1.25 holes for mounting a
variety of components. This fixture can be found below in Figure 17.
Most bosses and eyelets will be fixed with a simple rod coming out of the magnetic bases to guide the
cables, but at times this will need to be at an angle, so the last fixture shown below is a possible solution
that uses clamps to secure one rod to another at a certain angle, if needed. This fixture is shown below as
Figure 18 [14].
Figure 18. Magnetic base holder
Figure 17. Modular linear rail slider fixture front (left) and back (right) views
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Initial Technical Considerations
In evaluating the feasibility of the preliminary top concept shown in Figures 13-18 and its components,
one must consider the loads that each of these cable drag contributing components will see during cable
actuation. We know that these loads are fairly small in a static test set up when compared to riding loads.
Knowing this fact, the concept of locating each fixture with the magnetic bases shown in Figure 14 is a
feasible solution. Rated magnet pull loads, which are a measure of the force required to separate a
magnet from a ferrous plate, are around 220 lbf for the magnetic bases we have researched [12].
Appendix A includes a basic static analysis of a cantilevered magnet subject to an arbitrary load. This
analysis shows that the coefficient of friction plays a large role in how much of the rated pull load will
be achieved in a realistic application. However, steel on steel coefficients of friction, which is most
likely the contact scenario for the magnetic base surfaces, are between 0.5 and 0.8 [15]. Even with this
reduction in loading capacity from the rated pull force, the loading condition will still be smaller than
allowable.
In addition to magnet stability, stiffness and stability of each component is important to hold the cable
configuration in a position that is accurate of the routing geometry on an actual bike frame. Again, the
loads seen by each component will be small and should not appreciably deflect our components.
Intermediate Designs
Testing, research, and additional analysis were performed on our top design following the Preliminary
Design Review. While the four main subsystems: main base, fixture connections, force measurement,
and position control were still considered, different design options were added to each category. The
Preliminary Design main base option of a steel plate as the main base was eliminated when the weight
and additional cost of a thick ferrous base was brought into consideration. A six foot long piece of 1/4”
sheet steel did not seem like a very feasible design, thus a lower raw material cost and lower weight
alternative needed to be chosen. Testing on the magnetic bases was also performed following PDR.
Single Magnetic Base to Dual Magnetic Base Redesign
Following PDR, we ordered a magnetic base from McMaster Carr to see if the rated load of 220 lbf,
would in fact hold. Using the vertical positioning pole that screws into the M8 tapped hole of the
magnetic base, we used a fish scale to measure the necessary force to move the base from the steel plate.
Unfortunately, this testing proved what we feared. Utilizing one magnetic base, we found the tipping
force to be 12 lbf about the weak axis, and 17 lbf about the strong axis using a single magnetic base. The
intended use for the magnetic bases is to position dial indicators; therefore, said bases do not perform
well when a load is applied in the transverse direction. Both numbers were found with a lever arm of
10.5 inches, which is the most extreme height we expect a component to be mounted at. With this as our
baseline, we measured the force that is required to actuate a derailleur and a brake. By attaching a fish
scale to a cable, we found that the required shifting force was approximately 15 lbf, while the braking
force was 6 lbf, respectively. These loads were clearly too large for the single base design to function
properly.
With these results in mind, the notion of fortifying the magnetic bases came into play. Making each
single base into a dual magnetic base design with a steel plate connecting the two was designed to
increase stability. Flanges were welded onto the dual magnetic bases to increase stability in the weak
axis. Taking this design to the machine shop, we created a prototype and performed additional testing.
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While this performed better than the single magnetic base design, there were still stability issues.
Welding the flanges to a perfect 90 degrees proved harder than anticipated, and as a result, the flanges
actually did not add as much stability as we had hoped they would.
80/20 T-slot Design
Preliminary testing of the dual magnetic base design did not leave the team confident that they would
allow for accurate fixture positioning without tipping or sliding. An 80/20 T-slot design was developed
to achieve the goals and specifications of the project. With tipping and stiffness as main concerns, the T-
slot offered a stable base to mount fixtures. The flexibility needed to recreate new frame geometries was
also still present in this design. Figure 19, shown below, depicts the 80/20 T-slot design.
Figure 19. 80/20 T-slot design
The parallel rails would slide and be fixed in place using bolts to achieve any position in the x-direction.
The vertical struts would slide along the parallel rails, allowing for movement in the y-direction, while
the vertical component would give positional freedom in the z-direction. These three degrees of freedom
offer the flexibility necessary to recreate varying frame geometry. Corresponding fixtures to recreate all
the contact points on the bicycle frame were design to be mounted on the vertical struts and moved to
accurately create the “frame”. Custom lengths of 80/20 and all corresponding pieces could be ordered to
for our specific design. With the pieces coming in to specifications, the 80/20 T-slot design would
require no major manufacturing or machining.
After visiting Specialized and discussing both the magnetic base design and the T-slot design it was
decided that magnetic bases would fit the needs of Specialized’s test lab more closely. The main
concerns regarding this design were the robustness and life span of the extruded aluminum T-sot. The
aluminum T-slot was not seen as durable enough, as any drop hazard could possibly decommission the
entire system. Additionally, the amount of necessary fasteners to keep each individual component in
place was seen as a hindrance for the user. With these considerations in mind, we decided to put the
80/20 T-slot design on the backburner, as an alternative to the magnetic base design.
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Rotary Potentiometer Positioning System
Figure 20. Rotary Potentiometer
Initial positioning plans using a rotary potentiometer, seen above in Figure 20, worked in theory, but in
practice proved less than successful. Ideally, full XYZ coordinates could have been calculated from a
known radial distance and height of an object, paired with an angular displacement of the potentiometer.
A retractable clothes line was to be used to measure the radial length.
The potentiometer was expected to measure angular displacement. Since we need to have positional
accuracy to within one millimeter, we knew that we can have an error of only 0.25 degrees. We were
unable to get an accurate reading from the potentiometer as there was a dead zone at small angles. The
potentiometer would not accurately register any angle less than 30°, making this positioning system
inapplicable for a project where small angle changes were of the utmost importance. In addition to the
accuracy of the rotary potentiometer itself came the issue of the locating with a string. Precisely lining
the string up with the plate on the potentiometer was nearly impossible, and the point where the string
was measuring to was not the same as the angle that the potentiometer was registering. With these
issues, the rotary potentiometer option was ruled out for positioning.
Chapter 4. Description of Final Design After preliminary testing, extensive research, and hands on troubleshooting with internal cable routing, we
came to realize the difficulty associated with internally routed cables and the given intricacies. To
accommodate these difficulties, our final design allows for modularity in order to accurately recreate a
specified frame with unique geometry. Said design, seen below in Figure 21, employs dual magnetic bases
and mounted vertical slide assemblies. These magnetic bases are mounted to a steel table that Specialized
has in house in their testing lab. An inline load cell is used to measure the input tension while gear shift is
performed by the test operator. This force is recorded using a Data Acquisition System (DAQ) and
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LabVIEW software. The transient shifting force profile can be examined for various cable routing
configurations and post processing this data allowed us to determine the relative cable “drag” in the system.
The measured values were compared to a cable routing configuration known to have “good” cable drag.
Cable drag, or friction, is largely a subjective phenomenon, but this test bed will allow Specialized to
quantify drag before designing an entire bicycle frame. A complete drawing packet, comprising of all
assembly drawings and detailed part drawings, can be found in Appendix B.
Figure 21. Final Design Layout
Main Base The main base for the entire test set-up is a steel table located in the test lab at Specialized. The steel table
has T-slots running along its length that can provide additional mounting or clamping options if needed.
Additionally, a steel plate can be mounted to the current table used by Specialized if a cable configuration
would require a magnetic base to be located where there is a T-slot. Using Specialized’s thicker ferrous table
will ensure that the full pull force of the dual magnetic bases is achieved.
Dual Magnetic Base and Vertical Slide Dual magnetic bases, fortified with a steel connecting plate, are used to position hard points where a cable
comes in contact with a frame component. Galvanized sheet steel and bolts screwed into the M8 holes on the
top of the McMaster Carr magnetic bases offer increased stability. These dual magnetic bases also offer
modularity as they can be positioned anywhere on the x-y plane of the steel table. Adjustment in the vertical,
z-direction, can be achieved using manual vertical adjustment slides made by Generic Slides. The vertical
slides are mounted to the connecting plate through a rotary plate [16]. The rotary plate fixes to the dual
magnetic bases with a single screw through the bottom of the connecting plate. This allows rotation
about the vertical axis so that the strong axis of the magnetic base can be aligned in a manner that favorably
resists the tension force from the cable. The dual magnetic base, vertical slide, and rotary plate assembly is
shown below in Figure 22.
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Figure 22. Dual magnetic base assembly with vertical slide and rotary plate
Magnetic bases offer reliable mounting and resist the loads necessary to shift. The magnetic bases offer
quick adjustment as well, as the on/off switches make setting up the test a faster process.
With the maximum load applied to the vertical slide assemblies, a deflection of 0.75 millimeters can
occur. The vertical slides allow for easy positioning and mounting.
Fixtures
As initial research proved, there are many points on the bicycle frame that the cable comes in contact
with. These hard points were modeled in our design because they contribute to the overall cable drag in
an actual system. Components are custom to allow for modularity and geometries that do not
necessarily exist yet. For our design, we chose to focus on the main components to fix to the magnetic
base assemblies: handlebar mounting, cable stopping points, bottom bracket guide, derailleurs, and
brakes.
Handlebar Mimicking Fixture
The handlebar assembly designed to accommodate different handlebar geometries can be seen below in
Figure 23. The assembly is comprised of bicycle handlebars, a plate, cable stop fixtures, a load cell fixture,
and pin fixtures for positioning.
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Figure 23. Custom handlebar fixture in assembly and exploded views.
These modular handlebars allow for different geometries that have not been prototyped. Extending the reach
of the handlebars accommodates the in-line load cell that needs to be applied on a straight portion of cable.
On ordinary handlebars, there is not enough space to allow for the load cell fixture; these modified
handlebars with extended reach allow the load cell to move between the supports in a linear fashion.
Following the supports and load cell, there are cable stops and positioning pins. The stops represent where
the cable would normally come out of the shifter lever, while the pins would position the cable to follow the
bends that would normally occur in an internally routed handlebar. The cable can be easily fed around the
“pseudo-stem” into the rest of the system, while the applied force can be drawn from the load cell in the
custom handlebar fixture. This fixture includes two stock plastic brackets for fixing the cut handlebars, and
various bolts and nuts, the specifications for which can be found in Appendix B.
Stem Fixture
The stem fixture was designed to mount the handlebars. Attached to a vertical slide and dual magnetic
base assembly, the stem fixture allows the handlebars to hang off the table while the user runs the test.
The stem can be seen on the far left in Figure 23, connecting the custom handlebar fixture to a vertical
slide.
Cable Stops
Cable stop fixtures, as seen in Figure 24, are comprised of three main pieces, paired with various
fasteners: square tubing, brackets, and a custom cylindrical cable stopping point. Accurate recreation of
frame geometry is crucial to the testing environment, and this design allows for complete control of
position and the necessary six degrees of freedom.
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Figure 24. Cable stop fixture in assembled and exploded views
This cable stop fixture utilizes a one inch by one inch steel square tube on the outside. Inside the steel
square tube, there is a cylindrical bar stock of 13/16 inch steel with the dimensions of a given cable stop
milled near the end of it. The bar stock has a “counter bored” hole to ensure that any style cable stop or
other cable-frame interaction components will be able to work with the entire fixture.
Once the holes were drilled, the physical cable stop was placed into the bar stock, and the geometry of
the frame was recreated, without adding any additional support that the cable stop would not normally
provide. The cylindrical bar stock is capable of moving inwards and outwards, as well as rotating within
the square steel tube. The cylindrical bar stock and stop are held in place with bolts which can be
tightened down to lock the bar stock in place. The bolt fasteners work with a similar idea of how
Christmas tree holders work. The threaded wall of the square tube works in conjunction with the bolts
that will continue to thread until it hits the circular bar stock within, thus holding the stock into place.
Additionally, the square tubing is able to pivot about the through screw, supported by the brackets,
holding the square tube at the desired angle.
A single #10-32 screw runs through the two brackets and the square tube, secured on the opposite end
with a nut. With the brackets flush against the square tube, using one screw and nut, the fixture is secure
and easy to position. The in and out motion as well as rotation of the cylinder within the square tubing,
pivoting of the square tubing, vertical positioning of the slide, rotation of the rotary plate, and the x-y
positioning of the magnetic bases account for the six necessary degrees of freedom. The magnetic bases
drove the design of the stops positioning system, and can be easily integrated with the rest of the custom
fixtures used in the system with the magnetic bases.
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Bottom Bracket Guide
Figure 25. Bottom Bracket guide fixture in assembled and exploded views.
The design for the bottom bracket guide can be seen in Figure 25. The fixture is comprised of six pieces: two
support arms, a center fixture with mounting holes, a threaded rod, and two nuts. The design of this fixture is
to accept any bottom bracket guide and support it. We chose to use the two support arms because they can be
adjusted to any reasonably shaped bottom bracket guide and still support it at three points. A fully rigid
fixture would not be capable of adjusting to accept an oddly shaped bottom bracket guide. The two support
arms were 3-D printed using the Mechanical Engineering Department printer for prototyping.
Rear Derailleur Mounting Fixture
The rear derailleur fixture can be seen below in Figure 26. This fixture accommodates a derailleur hanger
which a rear derailleur can be attached to. Small washers and M3 screws are used to space and fasten the
derailleur hanger onto the fixture itself. The noodle block, attached with a C-clamp, can be positioned to
dictate the cable loop near the rear derailleur.
Figure 26. Rear derailleur fixture with noodle block
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Front Derailleur Mounting Fixture
The model for the front derailleur fixture can be found in Figure 27. The two holes allow for mounting
to a vertical slide assembly and the cylindrical section allows for a braze-on anchor (as seen in Figure
28) to be mounted. The braze-on anchor allows for the attachment of a front derailleur.
Figure 27. Front Derailleur Fixture
Figure 28. Braze-On Anchor
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Brake Fixture
Figure 29. Brake Fixture
The brake fixture is seen above in Figure 29. The back plate attaches to a vertical slide assembly with
four screws. The other piece of this design is simply a hole in the attached plate for mounting a caliper
rim break.
Analysis/Preliminary Testing
In order to verify that the current design will perform accurately and reliably, some basic hand
calculations were performed to estimate the performance of the system. We theoretically calculated the
tipping force of a single magnetic base after our first test run using magnetic bases (See Matlab code and
hand calculations in Appendix E). The theoretical calculations were similar to our testing results, both
showing that one magnetic base would not be able to handle the loads we expected during operation of
our test. The test results and analytically calculated tipping force for one magnetic base were then used
to develop a more accurate model for tipping in an updated dual magnetic base design, which is our final
design. However, upon testing, we found that sliding became the issue with the new dual base design.
Based on testing, the magnetic bases should be able to handle the required operation loads but sliding
will most likely be the first mode of failure. A full Failure Mode Effects Analysis can be found in
Appendix E. These were our main concerns for failure modes.
Dual Magnetic Base Analysis & Testing
McMaster Carr gives a rated magnetic pull force of 220 lbf for each of the chosen magnetic bases. Using
this fact, we theoretically predicted the tipping force to be around 80 lbf at a lever arm of 10 inches.
Additionally, we predicted that the sliding force would be approximately 100 lbf. These numbers are
much higher than our expected load of 20 lbf.
After actual testing, however, we found that the magnetic bases would slide at a force of 26 lbf along the
strong axis, and tip at 17 lbf along the weak axis, when a thin ferrous base is used. For a thick ferrous
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base, it took 30 lbf to tip along the strong axis, and 23 lbf to tip along the weak axis. Since these
numbers are greater than our expected loads of 20 lbf, we feel that the modified magnetic base design is
adequate for our application, provided that we design for aligning everything along the strong axes.
Should a specific configuration tip or slide a magnetic base, it would not be too much trouble to redesign
a base configuration that would resist sliding or tipping for the particular application.
Deflection Analysis
To ensure accuracy in positioning, we want to keep the deflection and bending of the vertical slide
fixtures to a minimum. In order to do so, we performed deflection analysis of the fixture, modeling it as
a cantilever beam. Complete analysis can be seen in Appendix E. From our results, we deduce that the
deflection is not concerning, as it would only deflect the assembly 0.75 mm.
Force Measurement
The force measurement system is comprised of a data acquisition system, a threaded load cell, and a
signal conditioner. The signal conditioner will take standard 110 Volt AC power as an input, and
outputs the correct excitation voltage for the load cell to function. The DAQ system is USB powered,
meaning that its power will be supplied by whatever computer or laptop system it is plugged into. A
supplied cable with leads will allow interaction between the signal conditioner and the DAQ box for
differential voltage readings to be used with LabVIEW.
Figure 30. NI-6001 USB DAQ
The data acquisition unit used is the NI- 6001 USB system from National Instruments, as seen in Figure
30 [17]. This DAQ system is both cost effective, at $189, and relatively simple. This is very cheap
compared to other DAQ systems, which can cost upwards of $1,000. This DAQ system also has a USB
plug in cable, which allows for easy access with computers and laptops, making it convenient for
testing. In order to get useful, comparative measurements from every test, the acquired data is post
processed in Matlab.
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Figure 31. Interface sealed stainless steel load cell
The threaded load cell that we have chosen is the Interface WMC sealed stainless steel load cell. This
can be seen above in Figure 31 [18]. This load cell is miniature in size and has two male threaded ends.
We decided on this load cell, as our design needed the brake or shifter cable to stay in line with the load
cell to get accurate measurements. The load cell assembly with the fixtures can be seen in Figure 32,
below. The size of the load cell was also a determining factor. We wanted to make sure that the load
cell was small enough that it does not contribute to the drag of the system and works with our given
application of tension in the cable.
Figure 32. Load Cell Assembly
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Figure 33. Interface SGA signal conditioner
In order to use the Interface load cell with the National Instruments DAQ, an amplifier/signal conditioner is
required. The load cell outputs millivolts, while the DAQ outputs volts. We chose to use the Interface SGA
Signal Conditioner, as seen in Figure 33 [19] above. This signal conditioner ensures that the millivolts from
the load cell become amplified in order to be within the working rage of the DAQ. An Interface signal
conditioner also eliminates compatibility issues, as both the load cell and the signal conditioner are Interface
products.
Positional Measurement
Positioning to ±1 millimeter proved a much more daunting task than initially anticipated. While we
tried multiple options for positional measurement, we were not able to get to the specified
accuracy. The high level of uncertainty in relative positioning has been deemed the main variable in
why the 1 millimeter tolerance was not achieved. Points on components such as the bottom bracket, rear
derailleur, cable stops, and handlebars we picked as common points that could easily be measured on
any frame. Although these points are consistent with each specific geometry, the error in precision was
still present, as each point was slightly different in the system versus the existing frame.
Following the rotary potentiometer method described in Chapter 3, the grid method was
implemented. The grid had its own limitations, though it proved to be more accurate than the
potentiometer system. Five millimeter increments were the smallest increment we could use for a grid
before it became illegible. We were able to get our positioning to within 17% error of the true
system. This was not within the specified 1 millimeter resolution. We believe that the error can be
attributed to the points on the components we picked, paired with the fact that 5 millimeters was the
most accurate grid that could be used.
Location and measurement in the vertical direction was dictated by the vertical slides. The necessary
accuracy and precision was provided by these instruments. Height gauges, in house at Specialized can
be used to measure the vertical positioning, but digital calipers were used for our purposes when testing.
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Chapter 5. Manufacturing
The following section outlines the manufacturing processes and assembly instructions for all parts and
fixtures being used. Some designs had to change slightly since the Critical Design Review and these
changes are noted in this section. The original schematic of the stock aluminum plate, which contains
the handlebar base, pseudo-stem, bottom bracket guide base, brake fixture, load cell supports, rear
derailleur fixture, and rotation plates can be found in Figure 34.
We quickly found that the ability to use any brand component (shifters, brakes, derailleurs, etc.) would
be a very difficult task. While the original goal was to create a system with modular fixtures to
accommodate any component with any geometry, we have determined that this was not a reasonable
goal for this project with the current magnetic base design.
The main change in the manufacturing plan from the Critical Design Review was that we chose to get
most of our parts manufactured by Water Jet Central instead of the previously planned CNC machining
in the Cal Poly machine shops. This option turned out to be less expensive and yielded a faster
turnaround than the CNC machining thanks to a generous discount by Water Jet Central. The only issue
we experienced with the water jet cut parts was the small draft angle that the parts have on them after
being cut. To fix this and create flat surfaces for welding, proper clearance holes, and holes for
threading, we had to face the surfaces of some of the parts and re-drill some of the holes. A DXF file
with the updated parts can be seen below in Figure 34.
Figure 34. Picture of final layout sent to be water jet cut
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Another difficulty that was found in the initial design was the welding done on the fixture pieces that
were water jet cut. In order to save time and money, all of the parts were water jet cut from the same half
inch thick 6061- T6 aluminum plate. However, many of the parts could have been made from thinner
material. The half inch thick aluminum provided challenges when it came to welding because the large
thickness required a lot of current, and made it very difficult to weld the material.
The welding professor at Cal Poly was able to complete the necessary welds with only minor difficulty
on the load cell supports, bottom bracket fixture, rear derailleur fixture, and two brake fixtures. We
planned to weld the stop fixtures to the handlebar fixture ourselves at a later date. Unfortunately, with
the thickness of the material, yet relatively small size of the stops, we were unable to follow through
with the intended plan. This forced us to fix it in a different way, thus we decided to thread a hole in the
bottom of the aluminum block and fix it from the underside of the handlebar fixture with a screw.
Main Base Plates
The main base plates were originally designed to be cut out of sheet steel with the holes machined in the
Cal Poly machine shop; however, due to the reliability and fast turnaround that was found with Water
Jet Central, we decided to have the main base plates water jet cut to save time. A DXF file of the main
base plates, sent to Water Jet Central can be seen below in Figure 35.
Figure 35. Picture of the 10 gauge steel main base plates
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Handlebar Mimicking Fixture
This design changed a lot from the previous design. The original handlebar fixture assembly, seen in
Figure 23, involves a variety of parts whose fabrication and assembly process is outlined in this section.
The main base and pseudo-stem of the handlebar fixture assembly were designed to be made from 2ft. x
1ft. x 1/2in stock aluminum plate and precision CNC milled at Cal Poly. This was one of the parts that
ended up being Water Jet cut with the rest of the parts and also had a few modifications made to it, as
seen in Figure 34. The main base of the handlebar fixture has six slots for positioning cable, four
through holes for mounting the pseudo-stem to the base, and four through holes for the clamps used to
mount the pieces of actual handlebar seen at the ends. The pseudo-stem has four through holes for
mounting to the base and four through holes for mounting to the vertical slide assembly.
The two cable stop fixtures that are seen to the left of each load cell fixture were manually milled from
stock aluminum bar. These were then supposed to be TIG welded to the flat plate base for accurate cable
positioning and tension measurement; however, as mentioned previously, these were fastened with a
bolt instead due to the difficulty of the welding.
The load cell fixtures were fabricated out of stock aluminum rod cut to size with a band saw. The upper
half of half the rod was milled away and then the holes drilled and threaded on the manual mill and the
whole thing assembled with a set screw and washer. Each load cell is supported with two aluminum
plates on either side to prevent sag or wobble that the weight of the load cell fixture causes. These plates
were also to be cut out of the stock aluminum plate using CNC milling along with the main base and
pseudo-stem and then TIG welded in place on the base plate but were water jet cut instead and then
welded as planned.
The slots are used with stock threaded rod and nuts to position the cable and housing coming out of the
fabricated cable stop fixtures. The rest of the assembly is completed by fixing the handlebar clamps,
stem, and stops with bolts and nuts. A picture of the entire assembly with all the described components
can be found below in Figure 36.
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Figure 36. Final assembled handlebar mimicking fixture
The handlebar fixture was the biggest limiting factor on our initial goals. Because of the complexity and
large variation in routing in the handlebar area on different bikes, it was very hard to create a fixture that
would work for all scenarios. For lower end bikes, the shifters are often not routed inside the handlebar
or under the bar tape which is not an issue because the cables can just be in free space with the cable
interaction points mounted as usual; however, with internally routed handlebars, the situation becomes
more complicated. This is where all the magic happens; the cable force is actuated through a shifter, the
load cell is attached in line and must move linearly without drooping, and the cable must take
complicated turns that are difficult to get the actual geometry for.
Although most shifters contribute a negligible amount of the drag to the cable just through the
mechanism, the different shifters provide their own complications because some shifters have different
geometries which are hard to accommodate with a single fixture. To keep the load cell in line with the
cable, our fixture was designed so that the cable interaction point at the shifter is separated by a length of
space where the load cell fixture resides (for a more detailed explanation of the design, reference the
handlebar mimicking fixture section in Chapter 4). This only allows for a shifter where the cable comes
straight out the back and down toward the bike. Some shifters have the cable exit the side and then take
a sharp turn down into the handlebars or out into free space like in some lower end bikes. This creates a
situation in which our fixture could does not work because we cannot accommodate that bend and
therefore cannot accurately simulate that situation.
Another problem is the fact that the load cell fixture is relatively heavy and hard to position correctly.
The weight of the load cell causes the whole cable to want to droop down which would result in an
inaccurate system. The load cell supports were added as a sort of bushing to prevent this, but this
obviously induces some extra friction. We believe that this is a large source of inaccuracy in the system
that results in slightly higher loads than the actual system would see. Our system is still accurate in the
35
comparison of two different frame geometries, however, because the same amount of drag would be
added by the load cell for each test.
Another slight issue with the load cell fixture is that it needs to be exactly in line with the cable. We
found that this was not quite achieved in our set-up because the welding of the load cell supports and the
placement of the handlebar stop were not perfectly in line with where the cable needed to be. This leads
to sideways forces on the load cell, pushing it up against the supports, causing additional drag. Again,
while this adds to the drag in the system, two different geometries can still be compared.
Actual Stem Fixture
For the actual stem and handlebar mounting fixture pictured in Figure 24, stock round aluminum bar
was cut with a band saw and material removed from either side with a manual mill here at Cal Poly so
that it can be fixed to a vertical slide assembly with two #10-32 screws for an actual stem to be mounted
on to the still circular part of the tube. Actual handlebars can be fixed to this stem and the cable routed to
get an actual feel for the system. This fixture take about one hour to fabricate
Cable Stop Fixture
The cable stop fixture assembly seen in Figure 25 was made from stock square steel tubing, stock round
aluminum bar, and two brackets. All of the machining for these fixtures was done by our team here at
the Cal Poly machine shops. Due to the specific dimensions on the bracket spacing and available square
tubing sizes, the brackets also needed to be slightly altered to achieve the correct spacing. A manual mill
was used to machine off sixty thousandths of an inch from the outer face (highlighted in Figure 37,
below) of each bracket.
36
Figure 37. Bracket for cable stop assembly, with face that needs material removed
The steel square tubing and aluminum bar was cut to size on a band saw. The aluminum rod was
machined on a manual mill to drill the hole on each side. Last, the square steel tube was machined on a
manual mill to drill and tap the hole on each face. The assembly for this fixture needed to be done in a
certain order due to the tight space that it operates in. The brackets were fastened to the vertical slide
assembly first with screws. The square tubing is then placed inside the brackets and the through bolt
inserted and tightened on the other side. The aluminum rod is then placed inside the steel tube and
tightened in place with the four bolts. These fixtures take about 5 hours to fabricate.
This design was carried out the way it was intended to and they allow for all six degrees of freedom as
discussed in the design section of this report. We believe they are capable of representing any frames
that Specialized may need. A picture of these finished assemblies can be found below in Figure 38.
37
Figure 38. Finished cable stop fixture assembly
Bottom Bracket Fixture
The bottom bracket guide pictured in Figure 26 was water jet cut from the same stock aluminum plate
used above for the handlebar mimicking fixture. Two pieces were to be cut out in the water jet process
and then TIG welded together. For the prototype, the “arms” seen below in Figure 39 that support the
cable guide were 3D printed using the 3D printer in the Cal Poly ME department; however, the final
design can still be fabricated using precision CNC milling on site at the Specialized headquarters.
38
Figure 39. Bottom bracket guide arm
The main body pieces that are welded together were machined on a manual mill before welding to drill
the long hole for the threaded rod while the four through holes on the back piece were created when
everything was water jet cut. Our final prototype does not have the threaded hole on the front to
accommodate the screw of a bottom bracket guide because we did not have access to a guide for testing
until the very end of testing and the size and position of those holes vary so much that we found it not
feasible to place just one threaded hole for any cable guide; however, the tension in the cables is
sufficient to hold a guide in place once it is positioned. The 3D printing took about 1 week to get all the
paperwork squared away and the process completed. The machining took thirty minutes and all the
welding about two days from when it was dropped off and picked up. A picture of the final prototype
can be found below in Figure 40.
39
Figure 40. Finished assembly of the bottom bracket guide
Main Base and Vertical Slide Assembly
The main bases seen in Figure 22 are composed of two magnetic bases and a flat plate with two
fasteners. The flat plate was water jet cut out of steel plate as mentioned above instead of being cut by
our team at the Cal Poly shops. The plate can be fixed to the mounting hole on each magnetic base by
the two outer holes and one more hole was cut in the flat plate directly in the middle to fasten the
vertical slide assembly from below. The square plate that allows rotation of the vertical slide assembly
was cut out of the same aluminum plate that was water jet cut for the handlebar assembly and the four
mounting holes for fastening the vertical slide assembly down tapped in the Cal Poly machine shops.
One more tapped hole was machined through the middle of this rotating plate to fasten it to the flat plate.
The drilled and tapped holes took about one hour to complete and the water jet parts took two days to
complete.
These components of our design have performed well in testing and we believe that they are sufficient
for the project goals that we wanted to meet. Getting the steel base plates water jet cut saved us a lot of
40
time in manufacturing because they were done in a day and delivered to us when we needed them for a
good price. These assemblies can be seen in Figures 38 and 40 above.
Rear Derailleur
Figure 41. Initial Design of Rear Derailleur Fixture
The initial rear derailleur fixture design, seen above in Figure 41 was designed to be manufactured by
our team at the Cal Poly machine shops. Instead of being machined in the CNC process, these parts were
also cut out in the water jet process and then welded together. The original design for this piece seen
above included a small piece of plastic that was to be placed onto the end of the perpendicular strut with
the single hole under the derailleur hanger being fixed there. This was to allow for structurally sound
mounting of the derailleur hanger which is what the rear derailleur attaches to. The derailleur hanger has
an oddly shaped cutout where it would normally sit on the right dropout and we are going to fill that
space with our plastic cut-out. Because this does not need to be perfectly accurate, we planned to trace
the shape onto a plastic sheet of acetal delrin and cut that out using a band saw. We instead ended with
the design seen in Figure 26 and did not need that plastic piece.
This rear derailleur fixture went through quite a bit of redesign and therefore manufacturing changes
after the critical design review. Figure 26 shows the final manufactured version of the rear derailleur
fixture. It is designed to accept any rear derailleur hanger and hold various rear derailleurs and was
fabricated through water jet cutting. The hanger mounting holes were bored on the drill press. This piece
is fixed to the vertical slide assemblies with 4 screws like the other fixtures. The manufacturing for this
part took about one hour. A picture of the finished assembly can be seen in Figure 42 below.
41
Figure 42. Completed rear derailleur fixture assembly
Front Derailleur
The front derailleur fixture, as seen in Figure 24, was fabricated in the exact same fashion as the fixture
for an actual stem for the handlebars and therefore had the same time estimates, as laid out above in the
actual stem fixture section. The front derailleur fixture was machined exactly as planned, but has not
been used or tested yet due to the reduction in the scope of this project. This piece took only about an
hour to fabricate.
Brake Fixture
The brake fixture pieces were cut out in the water jet process with all the other half inch aluminum. The
assembly can be seen in Figure 29. Similar to the bottom bracket fixture base, two squares of aluminum
plate were cut and then welded together as shown. The first piece has four through holes for bolting to
the vertical slide assembly with #10-32 screws while the second piece has a single through hole for
fixing a rim brake to it. Similarly to the front derailleur fixture, due to our reduction in scope, the brake
fixture was never used or tested in our system.
42
Chapter 6. Design Verification
In order to ensure a functioning test system to be used by Specialized, we wanted to verify that all
components work correctly, and all measures are taken in order to have successful test runs. We ran
various tests for our verification. The types of tests that were done were time tests, calibration tests, and
a comparison test. A Design Verification Plan and Report can be seen in Appendix G.
Time Tests
We wanted to ensure that set up and the operation of one test run would last no more than 30 minutes.
Unfortunately, the setup took longer than 30 minutes each time we tested. The amount of fasteners that
needed to be tightened, as well as adjusting the height of each component took time. Routing the cable
in our setup was also time consuming, as the cable needed to be fed a certain way in order for it to be
actuated properly.
Another test that we wanted to perform was to ensure that it takes no more than one hour for someone to
learn how to fully perform a testing run. We could not verify this test due to time constraints of the
project. We wanted to verify that the other aspects of the system worked before utilizing this test;
however, this test can be easily completed by a test engineer at Specialized.
Calibration Tests
We had two calibration tests for the equipment being used for our final system. Our final system
includes a load cell and a paper grid. To use the system, we needed to make sure that the load cell and
grid were correctly calibrated. In order to do so, we did comparative tests to known forces for the load
cell calibration, and we ensured that the grid was correctly printed. A series of loads were applied to the
load cell, and a best fit curve to the data was made. This data yielded a correct calibration of 5 volts to
30 pounds. This calibration curve can be seen in Appendix H.
Comparison Test
The most unique test performed was a comparison test for a good lever “feel” of the system setup. In
the bicycle industry, there are no set standards for expected forces for shifting and braking. Instead,
tests are done based on user input and how crisp a shift, or how complete a brake feels. In order to do a
comparison test, we had a user feel an actual bicycle setup that our system’s configuration simulated,
and then felt our system afterwards. The user then determined if the bicycle and our system gave the
same feel. From the tests that we ran, the different users felt that our system represented the correct feel
of the bicycle system.
Cost Analysis
A final cost analysis was performed for the final design. The grand total for the entire project came in at
$4,406. The entire test setup was initially proposed to be $6,417, but after altering the scope of the
project, this budget fell to the final number seen in Table 5. This design was more expensive than
anticipated, but high cost items such as the vertical slides and the magnetic bases drove the price up. As
seen below in Table 3, the vertical slides, at $439 and the magnetic bases, at $43 added the most to the
overall cost. Our team was hesitant to decide upon vertical slides simply because of price. After
conferring with Specialized, and weighing out the cost against time spent on manufacturing custom rails,
43
we were encouraged to use the vertical slides. Saving time on the manufacturing process and ensuring
consistency, was deemed more important than the steep price associated with the vertical slides.
Table 4 below, shows the final cost breakdown for the raw materials. A proposed budget for these raw
materials was $163 initially, but a final cost of $440 came in at the end. The increase to this section can
be attributed to the water-jet cutting that we employed. While this added additional cost to this section
of the budget, it saved time and money in the machining process. Lastly, the fasteners were initially
specified to cost $97 as the cost estimation utilized McMaster Carr pricing which gave bulk numbers for
fasteners. Not needing hundreds of each type of fastener, we purchased them locally, in the quantities
we needed, and had a grand total for fasteners of $53.
Table 3. Final Cost of Miscellaneous Items
Table 4. Final Cost of Raw Materials
Raw Material Quantity Price Total
Steel Square Tube 1"x 1" x 0.12" 1 $7.97 $7.97
6061 Aluminum Rod (5/8" diameter) 1 $3.68 $3.68
Brackets 10 $0.63 $6.30
6061 Aluminum Plate (1'x2'x1/2") 1 H20 Jet $324.00
Multipurpose 6061 Aluminum Bar (3/4"x1"x6") 1 $4.35 $4.35
Multipurpose 6061 Aluminum Rod (1"dia.x6") 1 $5.28 $5.28
Multipurpose 6061 Aluminum Rod (1.125"dia.x6") 1 $6.38 $6.38
11 GA. (.124 thick) Galvanized Steel Sheet (1'x4') 1 H20 Jet $80.00
Handlebar Clamp 2 $0.90 $1.80
$439.76
Table 5. Initial and Final Cost Estimates
Miscellaneous Quantity Price Total
Signal Conditioner-SGA 1 $345.00 $345.00
NI USB-6001 DAQ 1 $189.00 $0.00 (From Specialized)
Load Cell 1 $660.00 $660.00
Power Cord 1 $18.00 $18.00
Calibration 1 $75.00 $75.00
Vertical Slides 5 $439.00 $2,195.00
Magnetic Bases 10 $43.00 $430.00
Calipers 1 $190.00 $190.00
$3,913.00
Initial Projected Cost Final Cost
$6,416.98 $4,405.95
44
Safety Considerations
The dual magnetic base design offers the risk of pinching the user’s hand. The slight chance that the
magnetic base is turned on while a user’s appendage is under it is cause for concern. Additionally,
knowing the wear of the cable being tested is paramount. The risk of the cable snapping is also present,
but with careful monitoring, this risk can be mitigated. Aside from these two safety considerations, the
dual magnetic base design is a relatively safe design that if used properly, should not cause any user
harm while in operation. The Critical Hazard Checklist (Appendix I) shows that there are not any
extreme or pressing hazards associated with the dual magnetic base design. Additionally, the loads that
are seen by the system should not exceed 30 lbf. Thus, we did not find any further reason for safety
considerations with the relatively low loads applied.
Chapter 7. Management & Teamwork
After indicating the initial problem at hand, in-depth research was done to determine what causes cable
drag and to see what remedies that the current marketplace has. It was apparent that no product currently
exists on the market that could satisfy all the requirements set forth. The only alternative is to make an
actual prototype of the frame and route the cables through or around it to find the drag that is
experienced. This research led to the problem statement, giving direction and scope to the problem at
hand. Bicycle shop technicians offered insight into the complaints about cable drag and what type of
components add to the total degradation of performance. QFD was used to identify the customer groups
as well as the primary engineering requirements.
From the requirements and customer identification, we were then able to move into the conceptual
design portion of the project. Using techniques such as morphological matrices, brainstorming, and
brainwriting, numerous innovative ideas were explored and the validity of each was weighed out.
Working through the initial designs ideas, we were able to see which designs most effectively met the
design criteria. Pugh matrices were used to help sift through the ideation and determine the best possible
ideas for each subsystem of the entire product. After Pugh matrices for each subsystem were created, the
pairwise comparison method was used to find many different combinations of mounting fixtures,
creating accurate bends, and measuring force. All of the ideation has culminated in a few top ideas for
the design which are included with drawings and CAD models to give an idea of what our system ended
up looking like. A Gantt chart, as seen in Appendix F, shows the deadlines and phases that we saw fit to
complete the project by the Senior Expo in May of 2015.
A management plan was essential to successfully working through the design challenge in a timely
manner. To create a final product that meets all of the design criteria set forth by Specialized, we
formulated a structured management plan. This allowed each team member’s unique skill set to be used
to its fullest, while still allowing each individual to contribute to the project in full. Our management
plan aimed to allow individual team members who are either skilled or interested in a certain aspect of
the design process to lead the development of that area and to claim ownership of this category in the
final product within the team. This team management structure tasked each lead with ensuring the team
was on track with respect to his or her own area. In doing so, the team was able to meet all required
deliverable dates.
Information Gathering: Brandon Sadiarin
45
Prior art and patent search
Design and component research
Applicable features from other designs
Progress Documentation: Torey Kruisheer
Manage Weekly Updates
Project Records: budget, list of ideas, work completed
Report Consolidation: Torey Kruisheer
Compile individually created design documentation
Ensure quality of reports/documents: aesthetics, grammar, content
Engineering Analysis: George Rodriguez
Theoretical design analysis
Models and Detail Drawings: George Rodriguez
Create solid models: concept, prototype, production
Produce detailed component and assembly drawings
Compile complete B.O.M.
Simulation/Data Acquisition Lead: Brandon Sadiarin
Uncertainty/error propagation analysis
Test apparatus and simulation compatibility
Manufacturability Lead: Alex Powers
Machining, welding, and fabrication lead
Ensure manufacturability is considered in the design of all components
Evaluate and determine best manufacturing process for each component
Testing Plan: Alex Powers
Analyze test data to determine actions for improvement
Convey test data in intuitive and easy to understand way
Develop test methods to compare finished product to design requirements
The following timetable outlines the major deadlines scheduled for this project through its completion.
Table 6. List of major project milestones and their corresponding dates of completion
Project Milestone Date of Completion
Project Proposal 10/23/14
Preliminary Design Report 11/18/14
FMEA, DVP, Analysis Plan 11/25/14
Preliminary Design Review 12/5/14
Test Plan Development 1/14/15
Design Report 1/30/15
Critical Design Review 2/12/15
Manufacturing and Test Review 3/12/15
46
Project Hardware/Assembly Demo 4/23/15
Senior Project Expo 5/29/15
Final Report 6/5/15
To ensure adherence to each of the aforementioned deadlines, we reported our weekly progress to
Professor Sarah Harding. Weekly progress, outlined in a weekly status report, contained goals
completed for the previous week as well as projected goals for the current week. Additionally, we
conducted weekly telephone calls with Specialized in order to update our progress.
Chapter 8. Testing & Results
With the cable drag test system fully assembled, various tests were run to determine its performance.
Tests ranged from using a real Tarmac bicycle frame for system calibration to actuating the system with
a single shift using magnetic base assemblies for fixture positioning. The resulting test data confirmed
some design choices and matched expected system performance in some ways, while also falling short
of our expectations in others. The following figures and tables summarize over 50 tests that were
performed using the cable drag test system.
One important test that was performed was a comparison test between the system performance using a
real carbon Tarmac bicycle frame and the system we created to model the Tarmac frame’s geometry.
Figure 40 shows the resulting shifting loads for the real frame and system tests, respectively.
Figure 43. Real Tarmac frame and test system comparison
The required shifting tension for the real Tarmac frame was inexplicably higher than our test system
setup. Some of this difference can be attributed to the different initial pretension in the cable prior to
0 0.5 1 1.50
10
20
30
40
50
60
70
80
90
100
110
Cable Drag Test System Results
Time (s)
Fo
rce
(N
)
Tarmac Frame Test
System Tarmac Test
47
shifting. The black line on Figure 40 representing the Tarmac frame started with approximately 6
Newtons more tension force than our test system. We found throughout testing that an initial difference
in pretension will result in the same difference being measured in the maximum shifting force measured.
Tests were performed to attempt to verify this observation. Figure 41 below shows the effect of varying
pretension prior to shifting.
Figure 44. Effect of pretension on required tension force
Another main goal of this project was to be able to simulate cable drag differences for variable cable
geometry. In order to ensure that our test system would be able to capture these geometric differences
through differences in required cable tension, the geometry was varied and the cable tension was
measured. Figure 42 shows these results. The geometry was altered by moving the rear derailleur fixture
to a more drastically bent position.
0.4 0.6 0.8 1 1.2 1.4 1.60
10
20
30
40
50
60
70
80
90
Cable Drag Test System Results
Time (s)
Fo
rce
(N
)
Pretension Test 1
Pretension Test 3
Pretension Test 4
48
Figure 45. Difference in shifting profile based on varied cable geometry
The testing procedure can be found in Appendix K. This procedure outlines how a user would fully
setup, run, and analyze a test.
Chapter 9. Future Recommendations
While this project did not turn out exactly how we had hoped from the beginning, our struggles with
different designs and prototyping have given us tremendous insight into the problem at hand and what
can be done moving forward. Our team has created a system that can mimic a given frame geometry,
that actuates, and that properly measures the drag that a load cell “feels” while in line with a shifter
cable. Looking back on the project, there were some things done very well, and other things that
provided a learning experience. The primary issues that the team saw with the current design were with
the overall magnetic base design and the position measurement.
The magnetic bases were never quite as strong as the design said they should be due to poor surface
conditions and a generally weaker interface than what is advertised. If this project were to take a second
iteration, our team would suggest the use of stronger and controllable electro magnets. These were
researched initially, but were soon thrown out because of how expensive they would be. While they
would add to the expense of the project, electromagnets could create a much more accurate and reliable
system that could greatly benefit Specialized’s test team.
The position measurement portion of this project was an area where the Smooth Shifters felt that they
ran out of time to create the best design possible. While a few designs were experimented with, a truly
accurate system to the original design specifications was never developed. The team decided to settle for
a slightly less accurate method of using a grid with a plum bob on each cable interaction point to get as
close as possible to the necessary points so that a system could be tested to its full potential. The Smooth
Shifters feel that given more time, a better positioning system could be developed that could get the
entire test system within the desired tolerance of ±1mm.
0 0.5 1 1.50
10
20
30
40
50
60
70
80
90
100
110
Cable Drag Test System Results
Time (s)
Fo
rce
(N
)
System Altered Geometry
System Tarmac Geometry
49
Chapter 10. Conclusion
Knowing that high performance cyclists do not like the way that exposed brake cables look and knowing
that exposed cables also increase aerodynamic drag on the bicycle, internally routed cables have become
the new standard. Unfortunately, internally routed cables can potentially increase the drag experienced
by the rider because different cable housings and small bend radii decrease the performance. This is
detrimental to riders because shifting and braking becomes harder, resulting in a less than desirable lever
feel. Currently, Specialized lacks an accurate and efficient way to measure brake and shifter cable drag
with different configurations. The current system requires Specialized to prototype a bicycle frame and
route the cables before any drag measurements can be taken. This technique is not cost nor time
effective, as a new prototype has to be made whenever the drag of a different geometry setup needs to be
measured. Over the course of this project, the Smooth Shifters had hoped to deliver Specialized the most
effective cable drag test setup to satisfy the specifications set out above. This document serves to detail
the final progress and ideas, previous background research and decision making, in addition to
recommendations for where the project may be able to go next.
50
References
[1] Bikeman, "Cables & Housing," 13 May 2009. [Online]. Available:
http://www.bikeman.com/bicycle-repair-tech-info/1641-cables-a-housing. [Accessed 22 October
2014].
[2] D. Z. Chen.United States of America Patent US8783115 B2, 2014.
[3] K. R. Kozlowski and R. S. Shoberg, "Cable Tension Tester and Control System". United States of
America Patent US3943761 A, 16 March 1976.
[4] V. Agrawal, W. Peine and B. Yao, "Modeling of Transmission Characteristics Across a Cable-
Conduit System," Robotics, IEEE Transactions on , vol. 26, no. 5, pp. 914,924, 2010.
[5] [Online]. Available: http://cdn.velonews.competitor.com/files/2012/07/DSC01494-660x440.jpg.
[Accessed 17 November 2014].
[6] [Online]. Available: http://fcdn.roadbikereview.com/attachments/specialized/292231d1392674692-
converting-di2-specialized-owners-grommets.jpg. [Accessed 17 November 2014].
[7] [Online]. Available:
https://fairwheelbikes.com/assets/images/ashima_donuts_04_jpg/ashima_donuts_04.jpg. [Accessed
17 November 2014].
[8] [Online]. Available: http://cdn1.coresites.mpora.com/rcuk/wp-
content/uploads/2013/08/CavengeDropOut.jpg. [Accessed 17 November 2014].
[9] [Online]. Available: http://brimages.bikeboardmedia.netdna-cdn.com/wp-
content/uploads/2010/11/prototype-specialized-crux-cyclocross-bike-todd-wells3.jpg. [Accessed 17
November 2014].
[10] [Online]. Available:
http://service.specialized.com/collateral/ownersguide/new/assets/pdf/0000023579_R2.pdf.
[Accessed 17 Novemeber 2014].
[11] [Online]. Available: http://fcdn.roadbikereview.com/attachments/specialized/293698-demystifying-
hidden-cable-routing-new-specialized-1.jpg. [Accessed 17 November 2014].
[12] [Online]. Available: http://www.mcmaster.com/#magnetic-bases/=un95sx. [Accessed 17
Novemeber 2014].
[13] [Online]. [Accessed 17 November 2014].
[14] [Online]. Available: http://www.mcmaster.com/#magnetic-bases/=un99hq. [Accessed 17 November
2014].
[15] "Engineering Toolbox," [Online]. Available: http://www.engineeringtoolbox.com/friction-
coefficients-d_778.html. [Accessed 17 November 2014].
[16] "Vertical Slide Assemblies," [Online]. Available:
http://www.genericslides.com/vertical_slide_assemblies.html. [Accessed 12 October 2014].
[17] "Antronic," [Online]. Available: http://antronic.co.th/ProductDetail.php?Prd_ID=26. [Accessed 11
February 2015].
[18] "Interface," [Online]. Available: http://www.interfaceforce.com/index.php?WMC-Miniature-
Sealed-Stainless-Steel-Load-Cell-5-500-lbf-WMC-Miniature-Sealed-Stainless-Steel-Load-Cell-5-
500-lbf&mod=product&show=35. [Accessed 11 February 2015].
[19] "Interface," [Online]. Available: http://www.interfaceforce.com/index.php?SGA-Signal-
Conditioner-ACDC-Powered-Millivolt-to-Analog-Converter&mod=product&show=141. [Accessed
51
11 February 2015].
52
Appendix A
QFD
HOW:
Engineering
Specifications
WH
AT
: Cu
stomer
Req
uirem
ents
(explicit &
implicit)
1||||||
13%
15
21
91
02
1
2||||||
13%
15
12
90
03
2
3|||||||
16%
66
66
95
55
3
4||
5%
12
61
91
21
4
5|||
8%
13
51
94
13
5
6|
3%
11
11
94
02
6
7||||||
13%
15
11
90
00
7
8||
5%
12
21
90
00
8
9|||||||
16%
16
11
90
00
9
10
|||8%
13
41
90
00
10
13
# of Test Parameters
GUI
# of Inputs
Expandable libraries from test data
11
12
▲▲
Tra
nsp
ortable*
Mod
ula
r*
Mea
sure C
able F
orces*
Easy
to use/in
tuitiv
e test
Relia
bility
Life C
ycle
Bend Radius Tolerance
Max Weight
Max Size
Force Measurement Uncertainty
Time to Learn
Time to Perform One Test Set Up
Number of Runs Prior to Recalibration
Product Lifetime
○
Intu
itive U
ser Interfa
ce*
Accom
odates a
ll Req
uired
Inpu
ts*
Expan
dable
Tim
e to Ru
n
●
●○●
▽
●▽▽
▽○
●●
○
●●
○ ▽●
●
▽
●
●▽
○●
▽
● ▼
Riders
Relative Weight
Row #
Weight Chart
Direction
of Improv
emen
t
Colu
mn
#
50 lbf?
4' by 3'
+/- 1 N
1 Hour
15 Minutes
50 Tests
1000 Tests
1▼2
3
139.4
7
▲14
15
16
▼▼
▼▼
▼
268.4
2118.4
2139.4
7131.5
8165.7
960.5
26
134.2
1102.6
323.6
84
+/- 0.7 cm (find out through
testing)
4 Parameters
1.5 Minutes
yes/no
4 (dependent on most
important factors)
yes/no
71.0
53
94.7
37
142.1
1
| | | |
| | | |
| | | | |
|
| | | |
| | |
17%
7%
4%
6%
9%
9%
9%
8%
10%
4%
8%
6%
1%
12
34
56
7
| | | | | | | |
| | |2
41
12
30
Tech
nica
l Importa
nce R
atin
g
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9
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16
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53
01
89
10
11
12
13
99
99
99
99
9
▲▼
45
67
89
10
5
Row #
1
12
34
Our Current Product
Verizon Patent
Cable Tension Tester and Control System
0
99
| |
| |
| | | |
| | | |
0
02
11
03 1
50
00
0
51
00
0
00
00
0
Ou
r Cu
rrent P
rodu
ct
0
Max Computation Time (One Test Set Up)
Specialized
Bike Mechanics/ Technicians
Component Manufacturers
WH
O: C
ustom
ers
Tem
pla
te R
evisio
n: 0
.9 D
ate
: 4/2
3/2
010
Ch
ristoph
er B
attle
s
Current Product Assesment - Engineering Specifications
NO
W: C
urren
t Prod
uct A
ssesmen
t - Cu
stomer R
equ
iremen
ts
Maximum Relationship
3210
Verizon
Paten
t
Cable T
ension
Tester a
nd
Con
trol System
54
102
Ou
r Pro
du
ct
Co
mp
etitor #
1
Co
mp
etitor #
2
Co
mp
etitor #
3
Ou
r Pro
du
ct
Co
mp
etitor #
1
Co
mp
etitor #
2
Co
mp
etitor #
3
Co
mp
etitor #
4
53
Correlations
Positive +
Negative −
No
Correlation
Relationships
Strong ●
Moderate ○
Weak ▽
Direction of Improvement
Maximize ▲
Target ◇
Minimize ▼
54
Decision Matrices
55
56
57
58
Preliminary Drawings
59
60
Preliminary Analysis
61
Safety Design Checklist
• Will any part of the design create hazardous revolving, reciprocating, running, shearing,
punching, pressing, squeezing, drawing, cutting, rolling, mixing or similar action, including
pinch points and shear points?
• Pinch points at force actuation and points of derailleur movement
• Can any part of the design undergo high accelerations?
• No
• Will the system have any large moving masses or large forces?
• No
• Will the system produce a projectile?
• No
• Could the system fall under gravity creating injury?
• Yes
• Will a user be exposed to overhanging weights in the design?
• No
• Will the system have any sharp edges?
• No
• Will any part of the electrical systems not be grounded?
• No
• Will there be any large batteries or electrical voltage in the system above 40 V either AC or DC?
• No
• Will there be any stored energy in the system such as batteries, flywheels, hanging weights or
pressurized fluids?
• No
• Will there be any explosive or flammable liquids, gases, or dust fuel as part of the system?
• No
• Will the user of the design be required to exert any abnormal effort or physical posture during
the use of the design?
• No
• Will there be any materials known to be hazardous to humans involved in either the design or the
manufacturing of the design?
• No
• Can the system generate high levels of noise?
• No
• Will the device/system be exposed to extreme environmental conditions such as fog, humidity,
cold, high temperatures, etc?
• No
• Is it possible for the system to be used in an unsafe manner?
• No
• Will there be any other potential hazards not listed above?
• No
62
Actions List:
Hazard Corrective Actions Estimated
Completion Date
Actual
Completion Date
Pinch Points Warning labels 5/22/15
System
Falling
Ensure mounting table is securely
fastened 5/22/15 5/27/15
63
Appendix B
DRAWING NUMBERS LIST Fixtures
Bottom Bracket BB100-X00
BB Assembly BB100
BB Center Fixture BB200
BB Slide Arm Inner BB300
BB Slide Arm Outer BB400
Pseudo BB Guide BB500
Handlebars HB100-X00
HB Assembly HB100
HB Fixture Base HB200
HB Fixture Stem HB300
HB Fixture Stop HB400
HB Load Cell Support HB500
HB Fixture HB --
Load Cell Fixture LC200
HB Clamp --
Stops ST100-X00
Stop Assembly ST100
Stop Round Stock ST200
Stop Square Tube ST300
Stop Bracket ST400
Derailleurs F/RD100
Front Derailleur Guide FD100
Rear Derailleur Guide RD100
CNC Assembly CNC100 -X00
BB1 CNC100
BB2 CNC200
Brake1 CNC300
Brake2 CNC400
Vertical Slide Dual Assembly VS100 -X00
Vertical Slide Assembly VS100
Magnetic Base --
Magnetic Base Connecting Plate VS200
Vertical Slide Rotary Plate VS300
Vertical Slide --
Load Cell LC100-X00
Load Cell Assembly LC100
Load Cell Fixture LC200
Measurement AM100-X00
Angular Measurement System AM100
Rotary Potentiometer --
Lining Plate AM200
64
STOP FIXTURE
65
66
67
68
HANDLEBAR FIXTURE
69
70
71
72
73
BB GUIDE FIXTURE
74
75
76
77
78
FRONT DERAILLEUR FIXTURE
79
REAR DERAILLEUR FIXTURE
80
PARTS THAT NEED TO BE CNC MILLED
81
82
83
84
VERTICAL SLIDE ASSEMBLY
85
86
87
MEASUREMENT
88
89
LOAD CELL
90
91
Appendix C (List of Vendors) 1. Generic Slides
a. Phone: (412)492-7272
b. Fax: (412)492-7271
c. Email: [email protected]
d. 1049 William Flynn Highway Suite 300, Glenshaw, PA 15116
2. McMaster Carr
a. Phone: (562)692-5922
b. Fax: (562) 695-2323
c. Email: [email protected]
d. P.O. Box 54960, Los Angeles, CA 90054-0960
3. Interface, Inc. Corporation
a. Phone: (480)948-5555
b. Fax: (480) 948-1924
c. Email (SLO area): [email protected]
d. 7401 East Butherus Drive, Scottsdale, AZ 85260
4. National Instruments Corporation
a. Phone: (877) 387-0015
b. Email (California): [email protected]
c. 11500 N Mopac Expwy, Austin, TX 78759-3504
5. Metals Depot International
a. Phone: (859)745-2650
b. Fax: (859)745-0887
c. Email: [email protected]
d. 4200 Revilo Road, Winchester, KY 40391
92
Appendix D (Data Sheets)
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
Appendix E (analysis)
Hand Calculations
122
123
124
125
126
Matlab Code: Magnetic Base Analysis
clear all
close all
Display Parameter Figure pic = imread('BaseGeometry.jpg');
image(pic)
Double Base Parameters W = 7; %[lbf] Weight on center of magnetic base
Pm = 220; %[lbf] Rated pull load of single magnetic base
H = 10; %[in] Height load is applied at
l = 3; %[in] Depth of magnetic base in x-direction
a = 1; %[in] Flange extension length in x-direction
b = 2; %[in] Flange width in y-direction between magnetic bases
w = 2; %[in] Width of single magnetic base in y-direction
h = 3; %[in] Height of single magnetic base in z-direction
t = 1; %[in] Thickness of connecting plate
127
mu = .2; % Coefficient of Friction
Double Magnetic Base Analysis y-z plane
Fy_slide = mu*(2*Pm + W);
Fy_tip = Pm/H*(4/3*w + b/2);
% x-z plane
Fx_slide = mu*(2*Pm + W);
Fx_tip = (l/2 + a)*(2*Pm + W)/H;
Single Base Parameters W = 3; %[lbf] Weight on center of magnetic base
Pm = 440; %[lbf] Rated pull load of magnet
h = 10.5; %[in] Height load is applied at
l = 3; %[in] Critical width of magnetic base
a = 1; %[in] Flange extension length
Single Magnetic Base Analysis No "flange" assumption
F1 = l/(h)*(Pm/3.58 + W/2); % Allowable applied force [lbf]
M1 = W*l/2 + Pm*l/3.58; % Allowable resultant moment [lbf-in]
% % NOTE: modified equation above to match test results; experimentally 3.58
% % Should really be 3 theoretically
%
% % "Flange" assumption
F2 = (W*(l/2 + a) + Pm*(l/3.58 + a))*(1/h); % Allowable applied force [lbf]
M2 = (W*(l/2 + a) + Pm*(l/3.58 + a)); % Allowable resultant moment [lbf-in]
Print Results fprintf('\n*********Parameters*********\n')
fprintf('Total weight on base: %3.1f lbf \n',W)
fprintf('Rated pull load on base: %3.1f lbf\n',Pm)
fprintf('Critical width of magnetic base: %3.1f in.\n',l)
fprintf('Height of applied load: %3.1f in.\n',h)
128
fprintf('\n*******For no "flange" assumption*******\n')
fprintf('Allowable Force is %3.1f at %3.1f in. height\n',F1,h)
fprintf('Allowable Moment is %3.1f lbf-in\n',M1)
fprintf('\n******For "flange" assumption******\n')
fprintf('Allowable Force is %3.1f at %3.1f in. height\n',F2,h)
fprintf('Allowable Moment is %3.1f lbf-in\n',M2)
*********Parameters*********
Total weight on base: 3.0 lbf
Rated pull load on base: 440.0 lbf
Critical width of magnetic base: 3.0 in.
Height of applied load: 10.5 in.
*******For no "flange" assumption*******
Allowable Force is 35.5 at 10.5 in. height
Allowable Moment is 373.2 lbf-in
******For "flange" assumption******
Allowable Force is 77.7 at 10.5 in. height
Allowable Moment is 816.2 lbf-in
Plotting
Create mesh l_plot = linspace(1,8,50);
Pm_plot = linspace(100,400,50);
[l_plot,Pm_plot] = meshgrid(l_plot,Pm_plot);
M_plot = W*l_plot./2 + Pm_plot.*l_plot./3;
figure
surf(l_plot,Pm_plot,M_plot,'LineStyle','none')
colorbar
xlabel('l')
ylabel('Pm')
129
zlabel('M')
figure
contour(l_plot,Pm_plot,M_plot)
xlabel('l')
ylabel('Pm')
130
Design Failure Mode Effects and Analysis
Item / Function
Potential Failure Mode
Potential Effect(s) of Failure
Sev
Potential Cause(s) / Mechanism(s) of
Failure
Occu
r
Dete
c
RP
N
Recommended Action(s)
Load Cell Measurement
Disengaging
Loss of test /
inaccurate data
7 Insecure
Fixturing/Vibration 5 3 105
Close monitoring / Multiple tests /
Regular Recalibration
Breaking of Load Cell
Loss of test
7 Overuse/Dropping
onto floor 2 4 56
Close monitoring / Multiple tests /
Regular Recalibration
Decalibration Inaccurate
data 2 General use 2 4 16
Check calibration regularly against
known set up
131
Component Fixtures
Deflection Inaccurate
data 7 Tensioning cable 6 6 252 Testing / Analysis
Shearing of threads
Loss of test
7 Overloading 2 1 14 Testing / Analysis
Fatigue Inaccurate
data 7 Many tests over time 2 3 42 Analysis
Cable
Slack Inaccurate
data 2
Overuse / degradation over time / inappropriate setup
1 6 12
Have appropriate setup, and
regularly check for slack and loose points
No actuation Loss of
test 5 Inappropriate setup 1 3 15
Regularly check setup
Broken Inaccurate
data 3
Overuse / Over loading
2 1 6 Avoid
unnecessary loads
Base
Inaccuracy of Potentiometer
reading
Inaccurate positioning
6 Decalibration 3 1 18 Check calibration regularly against
known set up
Misalignment of positioning
device (height sensor and
potentiometer)
Inaccurate positioning
5 Decalibration 5 1 25 Regular
Recalibration
Breaking of potentiometer
Inability to position
6 Overuse/degradation
over time 2 4 48
Replace potentiometer
when necessary
Slack in measuring
string
Inaccurate positioning
2 Decalibration 1 6 12 Regularly check
setup
Breaking of Height Sensor
Inability to position
6 Overuse/degradation
over time 2 4 48
Replace height sensor when necessary
Inaccuracy of Height Sensor
reading
Inaccurate positioning
5 Decalibration 5 1 25 Regular
Recalibration
132
Breaking of measuring
string
Inability to position
5 Overuse/degradation
over time 2 4 40
Replace string when necessary
Magnetic Base Fixture
Pulling off base Loss of
test 7 Overloading 1 6 42
Avoid unnecessary
loads
Sliding across base
Loss of test
7 Overloading 1 6 42 Avoid
unnecessary loads
Tipping Loss of
Test 7 Overloading 5 6 210
Avoid unnecessary
loads
133
Appendix F (Gantt Chart)
.
134
Appendix G (DVP&R)
TEST PLAN
Item No
Specification or Clause Reference Test Description Acceptance
Criteria Test
Responsibility Test
Stage
1 Time to Set up and Perform
Test Measure time it takes to set up
and perform one run Less than 30 min Team PV
2 Time to learn how to use Teach a test engineer how to
perform tests and average times Less than 1 hour Team PV
3 Position measurement
calibration
Ensure positioning measurement device is correctly calibrated
prior to start
Ensure grid is printed correctly
Brandon and George
CV/DV
4 Position measurement
resolution
Ensure positioning measurement device has a fine enough
tolerance Less than 1 mm
Brandon and George
CV/DV
5 Force measurement
calibration
Ensure force measurement device is correctly calibrated
prior to start
Ensure a 30 pound force
corresponds to a 5 volt reading
Team DV
6 Force measurement resolution Ensure force measurement device has a fine enough
tolerance Less than 1 N Team DV
7 # of runs before load cell
recalibration Do 50 runs and ensure no
accuracy is lost More than 50
runs Brandon PV
8 Correct simulation Ensure setup has correct "feel"
when being operated
Comparative analysis with a Tarmac bicycle
frame setup
Team PV
135
TEST REPORT
SAMPLES TESTED
TIMING TEST RESULTS
NOTES Item no
Quantity Type Start date
Finish date
Test Result Quantity
Pass Quantity
Fail
1 50 C 4/25/15 5/20/15 more than 30 minutes
50
It takes more than 30 minutes to set up. Problems included
positioning bases, and routing cable
2 C 4/25/15 5/20/15 TBD
3
2 A/B 2/28/15 3/12/15 17% Error 1 1
First test was likely fine. Second test had
slip ups on measurements-
accidental repositioning of components.
4
2 A/B 2/28/15 3/12/15 see notes 2
(qualitatively)
Despite the grid having 5 mm ticks, it seems
that we can be accurate to 1 mm.
5
5 B 3/23/15 4/14/15 30 lbf
corresponds to 5.0144 V
4 0
weight of the load cell seems to contribute to the 0.0144 offset of the
expected 5.0 Volts
6
14 B 3/23/15 4/14/15 1.0 V
corresponds to 0.037 N
14 0
Load cell reads out the level of millivolts, which corresponds to
a fraction of a Newton- well within the
tolerance of 1 N
7
50 C 4/25/15 5/20/15 All results
have similar results
Since results are similar, it can be assumed that the accuracy stays.
8 20 C 4/25/15 5/20/15
The test has a correct
feel 20
The test feels correct when shifting.
136
Appendix H (Load Cell Calibration)
Pound Voltage
0 0.0044
15 2.5094
30 5.0144
Pound = 0.167Voltage + 0.0044
0
0.5
1
1.5
2
2.5
3
3.5
0 5 10 15 20
Series1
Linear (Series1)
137
Appendix I (Safety Checklist)
138
Appendix J (Bill of Materials)
Fixtures 2000
BB 2100
BB Center Fixture 2101
BB Slide Arm Inner 2102
BB Slide Arm Outer 2103
Pseudo BB Guide 2104
Stops 2200
Square Tube 2201
Round Stock 2202
Brackets 2203
Rear Der. 2300
Front Der. 2400
HB 2500
HB Fixture Base 2501
HB Fixture Stem 2502
HB Fixture Stop 2503
HB Load Cell Support 2504
HB Fixture HB 2505
Load Cell Fixture 2506
HB Clamp 2507
Vertical Slides 3000
Magnetic Base 3001
Magnetic Base Connecting Plate 3002
Vertical Slide Rotary Plate 3003
Vertical Slide 3004
Vertical Slider Carriage 3005
Miscellaneous 7000
WMC Sealed Stainless Steel Load Cell 7001
Load Cell Fixture 7002
SGA Signal Conditioner 7003
Potentiometer 7004
Potentiometer Plate 7005
Retractable Clothesline 7006
NI 6001 USB DAQ 7007
Metric Fasteners/Nuts 8000
M8 x 1.25 x 16mm Socket Button Head Cap Screw 8001
M8 x 1.25 x 12mm Socket Button Head Cap Screw 8002
M5 x 0.8 x 8 mm Socket Button Head Cap Screw 8003
Washers 8300
Plain Washer, 8 mm, Regular 8301
5 mm Plain Washer 8302
English Fasteners/Nuts 9000
139
Fasteners 9100
#10-32 4" Threaded Rod 9101
#10-32 x 0.5 Socket Button Head Cap Screw 9102
1/4-20 x .5 Socket Button Head Cap Screw 9103
1/4-20 x .875 Socket Button Head Cap Screw 9104
#10-32 x 1.5 Socket Button Head Cap Screw 9105
1/4-20 x 2.5 Machine Screw 9106
#8-32 x 1 Socket Button Head Cap Screw 9107
#10-32 x 1.75 Socket Button Head Cap Screw 9108
1/4 - 28 x .375 Stainless Steel Cap Screw 9109
Nuts 9200
#10-32 Machine Screw Hex Nut 9201
#8-32 Machine Screw Hex Nut 9202
1/4-20 Machine Screw Hex Nut 9203
140
Appendix K (Procedure)
1. Determine specified “hard contact” geometry points via Solidworks/equivalent CAD software.
2. Plot these points on the 5 mm incremented grid.
3. Print grid and decided points from CAD using a plotter.
4. Fix plotted grid to steel table, using clamps, to ensure accurate measurement (may need to
remove paper grid from underneath magnetic bases).
5. Measure the distance of cable necessary from the hand shifter to the load cell on the faux
handlebars.
a. Cut the cable in two.
b. Using the screw and nut, secure each end of the cut cable into the load cell fixture,
ensuring the cable is in line on either end of the load cell.
6. Mount each fixture to the carriage of the vertical slide using #10-32 x ¾” screws
7. Generally position each fixture in the z-direction:
a. Use adjustment wheel on the top of the vertical slide to dictate height
b. Lock the vertical slide in place using the lever on the top right of the slide
141
8. Line up the dual magnetic bases for each respective fixture using the grid and plotted position
points
a. Turn on the magnetic bases, securing the system to the steel table
9. Adjust/secure the rotation of the vertical slide using the M6 socket head screw located under the
vertical slide, between the magnetic bases
a. Adjust the vertical slide to ensure that the cable will run along the strong axis of the dual
magnetic bases, preventing tipping
10. Fine adjustment of faux handlebars:
142
a. Adjust the pegs on the faux handlebars to represent the desired path where the cable will
travel.
b. Ensure stability of handlebars on dual magnetic base fixture by also supporting the
hanging handlebars using a roller support stand (seen below)
11. Fine adjustment of cable stop fixtures:
a. Using the #10-32 screw and wing nut, secure the steel tubing at the desired angle
b. Adjust the inner cylinder, which dictates the distance and angle of the ferrule and
corresponding cable
c. Secure the inner cylinder with the thumb screws
12. Fine adjustment of the bottom bracket guide fixture:
a. Adjust and position the arms to accept the desired bottom bracket guide
b. Secure this position with the two nuts on either end of the threaded #10-24 rod
13. Fine adjustment of the rear derailleur fixture:
a. Position the “noodle” stop block using the slot and
b. Secure when the desired bend radius coming out of the rear derailleur is achieved
14. Feed the cable through each positioned fixture
a. Include cable housing where necessary
15. Initialize Labview with the “Cable Drag” vi (virtual instrument)
16. Connect load cell wires into the data acquisition unit
a. plug red striped lead into the a0 +port
b. plug solid red lead into the a0- port
17. Plug in power supply for load cell, and plug in data acquisition unit into computer
18. In the “Cable Drag” block diagram, adjust the DAQ assistant as necessary
a. Single up shift - 100k samples, and scan rate of 10-12k
b. Single up and down shift - 100k samples, and a scan rate of 10-12 k
c. Full up and down shift - 200k samples, with a scan rate of 10k
143
19. In the “Cable Drag” front panel, adjust the time axis of the graph by right clicking the graph
display, going to x scale, and going to properties
a. Single shift - 7 seconds max
b. Single up and down shift - 15 seconds max
c. Full up and down shift- 20 seconds max
20. Initialize a test in Labview, and then proceed to actuate the cable via the hand shifter/brake found
on the handlebar assembly
a. a graph of the data can be seen in the Labview front panel of the VI
b. Wait approximate three seconds before cable actuation
c. Actuate via shifter/brake mechanism found on handlebar assembly
21. Wait for a prompt to save
a. Save as a temporary name first (e.g. “1”, “2”, “a”, or similar)
b. pause the run until data acquisition is completed
144
c. Abort the execution in Labview
d. Rename the saved excel file as desired
22. Import data into Matlab file
23. Follow procedure in Matlab file to compare data
a. Have one file for a datum data set
b. Have other files as deemed necessary
c. Follow instructions for peak value outputs, curve smoothing, etc
145
24. Repeat process as necessary for different frame geometries